Aluminum alloys
Aluminum is of enormous importance in industry due to its increased ductility, high level of thermal and electrical conductivity, and low corrosion, since the Al2O3 film formed on the surface acts as a protector against oxidation.
Aluminum produces excellent thin rolled products, foil, and profiles of any shape using pressing and other types of pressure processing.
It is used to create various types of wires used in electrical equipment. Aluminum, like iron, is very rarely used in its pure form.
To give them the desired useful qualities, small amounts (no more than 1%) of other elements, called alloying elements, are added in production. In this way, alloys of iron, aluminum and other metals are obtained.
Physical parameters of aluminum alloys
Aluminum alloys have a density that differs slightly from the density of pure metal (2.7 g/cm3). It ranges from 2.65 g/cm3 for the AMg6 alloy to 2.85 g/cm3 for the V95 alloy. The alloying procedure has almost no effect on the elastic modulus and shear modulus. For example, the modulus of elasticity of strengthened duralumin D16T is almost the same as the modulus of elasticity of pure metal A5 (E = 7100 kgf/mm2).
However, due to the fact that the maximum fluidity of the alloys is several units higher than the maximum fluidity of pure aluminum, aluminum alloys can already be used as a structural material with different levels of loads (it all depends on the brand of the alloy and its condition).
Due to the low density index, the specific values of the maximum strength, maximum fluidity and elastic modulus (the corresponding parameters divided by the density value) for strong aluminum alloys can be compared with the same specific values for steel and titanium alloys. This makes it possible for aluminum alloys with high strength to compete with steel and titanium, but only up to temperatures not exceeding 200 C.
Most aluminum alloys are characterized by worse electrical and thermal conductivity, corrosion resistance and weldability in comparison with pure aluminum. It is known that alloys with a higher degree of alloying are characterized by significantly lower electrical and thermal conductivity. These indicators are directly dependent on the state of the alloy.
The best corrosion properties of aluminum alloys are observed in the alloys AMts, AMg, AD31, and the worst are observed in the high-strength alloys D16, V95, AK. In addition, the corrosion performance of heat-strengthened alloys largely depends on the quenching and aging regime. For example, alloy D16 is most often used in a naturally aged state.
However, at temperatures above 80°C its corrosion performance is significantly reduced and artificial aging is often used for use at higher temperatures.
AMts and Amg alloys lend themselves well to all types of welding. During the welding process of cold-worked steel, annealing is carried out in the area of the weld seam; for this reason, the strength of the seam is equal to the strength of the base material in the annealed state.
Types of aluminum alloys
Today the production of aluminum alloys is very developed. There are two types of aluminum alloys:
- deformable, from which they create sheets, pipes, profiles, packages, stampings
- foundries from which shaped casting is carried out.
The widespread use of aluminum alloys is due to their properties. Such alloys are very popular in aviation, automotive industry, shipbuilding and other areas of the national economy. Non-strengthening alloys Al - Mn (AMts) and Al - Mg (AMg) are corrosion-resistant materials from which gas tanks, oil tanks, and ship hulls are made.
Hardenable alloys Al - Mg - Si (AB, AD31, AD33) are used to create blades and parts for helicopter cabins, seaplane wheel drums. An alloy of aluminum and copper - duralumin or duralumin. The alloy with silicon is called silumin. An alloy with manganese - AMts has increased corrosion resistance.
Elements such as Ni, Ti, Cr, Fe in the alloy help to increase the heat resistance of the alloys, inhibit the diffusion process, and the presence of lithium and beryllium increases the elastic modulus.
Heat-resistant aluminum alloys of the Al - Cu - Mn (D20, D21) and Al - Cu - Mg - Fe - Ni (AK - 4 - 1) systems are used to create pistons, cylinder heads, disks, compressor blades and other parts that need to function at temperatures up to 300°C. Heat resistance can be achieved by alloying Ni, Fe, Ti, (D20, D21, AK - 4 - 1). Cast aluminum alloys are used to create cast workpieces.
These are the alloys Al – Si (silumin), Al – Cu (duralumin), Al – Mg (Amg). Among silumins, it is worth noting the alloys Al – Si (AL – 2), Al – Si – Mg (AL – 4, AL – 9, AL – 34), strengthened by heat treatment. Silumins lend themselves well to casting, as well as cutting and welding; they can also be anodized and even impregnated with varnishes.
High-strength and heat-resistant cast alloys of the Al – Cu – Mn (AL – 19), Al – Cu – Mn – Ni (AL – 33), Al – Si – Cu – Mg (AL – 3, AL – 5) systems. Those that have undergone an alloying process with chromium, nickel, chlorine or zinc can withstand temperatures up to 300°C. They are used to create pistons, block heads, and cylinders.
Sintered aluminum powder (SAP) is produced by pressing aluminum powder (700 MPa) at a temperature of 500 to 600°C. SAP is characterized by increased strength and heat resistance levels up to 500°C.
Aluminum alloy grades
Certain characteristics of aluminum alloys correspond to specific grades of these alloys.
Recognized international and national standards (formerly there were German DIN, and today European EN, American ASTM and international ISO), as well as Russian GOSTs, consider pure aluminum and its alloys separately. According to these documents, pure aluminum is divided into grades, and not into alloys. All grades of aluminum are divided into:
- high purity aluminum (99.95%)
- technical aluminum containing about 1% impurities or additives.
The EN 573-3 standard defines different purity versions of aluminum, for example, “aluminium EN AW 1050A”, and aluminum alloys, for example, “alloy EN AW 6060”. At the same time, aluminum is often called an alloy, for example, “aluminum alloy 1050A”.
In Russian standards, for example, in the document GOST 4784-97 “Aluminium and wrought aluminum alloys” and other documents on aluminum and aluminum alloys, instead of the term “designation” the similar term “grade” is used, only in the English equivalent “grade”. According to existing standards, you need to use phrases like “AD0 grade aluminum” and “AD31 grade aluminum alloy.”
However, often the term “grade” is used only for aluminum, and aluminum alloys are simply called “aluminum alloys” without any brands, for example, “AD31 aluminum alloy”. Sometimes people confuse the term “grade” with the term “marking”. GOST 2.314-68 defines the term marking as a set of signs characterizing a product, for example, designation, code, batch (series) number, production date, company trademark.
In this case, the brand is an installation or transport designation. Consequently, the designation or grade of the alloy is just a small part of the marking, but not the marking itself. The grade of aluminum or alloy is applied to one of the ends of the ingot or pig. Using indelible paint, colored stripes are applied, which serve as markings. For example, according to GOST 11069-2001, A995 grade aluminum is marked with four green vertical stripes.
According to the document GOST 11069-2001, aluminum grades are designated by numbers after the decimal point in the percentage of aluminum: A999, A995, A99, A85, A8, A7, A6, A5 and A0. At the same time, the purest aluminum is A999, which contains 99.999% aluminum. It is used for laboratory experiments. In the industrial sector, aluminum of high purity is used - from 99.95 to 99.995% and technical purity - from 99.0 to 99.85%.
Conditions (processing) of semi-finished products from deformable aluminum alloys MarkingCondition, purpose| Russia | USA | |
| Without maintenance | F | After manufacturing, without additional heat treatment. The degree of cold hardening and mechanical properties are not controlled |
| GK | – | Hot rolled |
| GP | – | Hot pressed |
| M | ABOUT | Annealed (soft). Highest ductility and dimensional stability |
| N | – | Cold-worked (cold-worked) |
| H4 | H18 | Heavily cold-worked (by rolling sheets about 20% for maximum hardening) |
| H3 | H16 | Three-quarters (3/4) cold-worked, increased strength |
| H2 (P) | H14 | Semi-hardened (1/2), increased strength |
| H1 | H12 | One-quarter (1/4) cold-worked, increased strength |
| Z | W | Hardened* (unstable, the duration of natural aging after hardening is usually indicated), increased strength |
| T | T3, T4 | Tempered + naturally aged. Obtaining sufficiently high strength, increased ductility, crack resistance, and fatigue resistance |
| T1 | T6 | Hardened + artificially aged for maximum strength |
| T12 | T77 | Tempered + artificially aged. Improving the characteristics of corrosion resistance, crack resistance, ductility with a slight decrease in strength. In Russian markings, an increase in the first digit of a letter indicates an increase in the degree of overaging and softening |
| T2 | T76 | |
| T3 | T73 | |
| TN** | T31, T36, T37, T39 | Tempered + naturally aged + cold-hardened. The second number indicates the degree of cold hardening deformation. Increasing strength while reducing plasticity and crack resistance characteristics |
| T1N** | T81, T83, T86, T87 | Hardened + cold-hardened + artificially aged. The degree of deformation (hardening) is indicated by the second number. Strengthening |
| Т1Н1** | T9 | Tempered + artificially aged + cold-hardened. Increased strength, especially when combined with the forming process of the part |
Source: http://mining-prom.ru/cvetmet/alyuminiy/alyuminievye-splavy/
Features and scope of application of aluminum alloys
Aluminum alloys are popular in various fields. Metal and mixtures based on it are among the top 5 most common on earth. When making parts, wires or housings from this material, it is important to understand what types of aluminum alloys exist and how they are classified.
Characteristics of aluminum
To understand what properties aluminum alloys have, you need to know the characteristics of the base material. It is a light and shiny metal. Aluminum conducts heat and electricity well, which is why wires and various radio components are made from it. Due to its low melting point, it is not used in highly heated structures.
Aluminum is protected on top by an oxide film, which protects the material from the destructive effects of environmental factors. In nature, this metal is found in rocks. To improve the characteristics of aluminum, other materials are added to it to create better mixtures.
The composition of aluminum and its alloys determines the characteristics of finished products. Most often, copper, manganese and magnesium are added to this metal.
The melting point of aluminum is 660 degrees Celsius. Compared to other metals, this is a low indicator, which limits the scope of the metal. To increase its heat resistance, iron is added to it. Additionally, manganese and magnesium are added to the alloy. These components increase the strength of the finished composition. The result is an alloy known as “duralumin”.
Separately, we need to talk about how magnesium affects the characteristics of the alloy:
- An aluminum alloy with a large amount of magnesium will have a high strength index. However, its corrosion resistance will be significantly reduced.
- The optimal amount of magnesium in the composition is 6%. This way you can avoid surfaces becoming rusty and cracks appearing during active use.
A mixture of manganese and aluminum makes it possible to obtain a material that cannot be processed by thermal methods. Hardening will not change the structure of the metal and its characteristics.
To achieve maximum strength without sacrificing corrosion resistance, mixtures of aluminum, zinc and magnesium are made. Alloy Features:
- The strength index can be increased using heat treatment.
- Electricity must not be passed through blanks made from this mixture. This is due to the fact that after passing current, resistance to corrosion processes will deteriorate.
- To increase resistance to the formation and development of corrosion, copper is added to the aluminum alloy.
Iron, titanium or silicon can also be added to the base material. New components change the melting point, strength index, fluidity, ductility, electrical conductivity and corrosion resistance.
Aluminum production
In nature, aluminum can be found in rocks. Bauxite is considered the most saturated. The production of this metal can be divided into several stages:
- First of all, the ore is crushed and dried.
- The resulting mass is heated over steam.
- The treated mixture is poured into alkali. During this process, aluminum oxides are released from it.
- The composition is thoroughly mixed.
- Next, the resulting alumina is exposed to electric current. Its power reaches 400 kA.
The last step is casting aluminum into molds. At this point, various components can be added to the composition that change its characteristics.
Features of alloy classification
Aluminum-based alloys make it possible to more efficiently use the base material and expand the scope of its application. Various types of metals are used to change characteristics. Iron or titanium is rarely added.
Aluminum alloys are divided into two large groups:
- Foundries. Fluidity is improved by adding silicon to the composition. Molten metal is poured into pre-prepared molds.
- Deformable. Ingots are initially made from these mixtures, after which they are given the required shape using special equipment.
Technical aluminum is included in a separate group. It is a material that contains less than 1% of foreign impurities and components. Because of this, an oxide film forms on the surface of the metal, which protects it from environmental factors. However, the strength of technical metal is low.
Ingots are processed using different methods. It depends on what shape you want to get after processing. Technological processes:
- Rolling. The method is used in the production of foil and solid sheets.
- Forging. A technological process by which parts of complex shapes are manufactured.
- Molding. Also used for making workpieces of complex shapes.
- Pressing. This is how pipes, profiles and rods are made.
Additionally, to improve performance, the metal is subjected to heat treatment.
Extruded aluminum alloy profiles
Grades of aluminum and aluminum alloys
Aluminum alloys are designated according to GOST 4784-97. The state document indicates the marking of aluminum alloys, consisting of letters and numbers. Explanation:
- D - this letter stands for duralumin.
- AK - marking of aluminum alloys processed during the forging process.
- A—denotes technical material.
- AB - avial.
- AL - designation of cast metal.
- AMts is a grade of aluminum with the addition of manganese.
- B is an alloy with a high strength index.
- SAP - powders sintered in prepared molds.
- AMg - mixtures with added magnesium.
- SAS - sintered alloys.
After the letter designation there is a number that indicates the grade of aluminum. A letter is indicated after the numbers. You can read a detailed explanation of the numbers in GOST.
Types and properties of aluminum alloys
When working with this metal and mixtures based on it, it is important to know the properties of aluminum alloys. The scope of application of the material and its characteristics will depend on this. The classification of aluminum alloys is given above. The most popular types of alloys and their properties will be described below.
Aluminum-magnesium alloys
Aluminum-magnesium alloys have high strength and are easy to weld. No additional component is added to the composition more than 6%. Otherwise, the material’s resistance to corrosion processes deteriorates. To further increase strength without sacrificing corrosion protection, aluminum alloys are diluted with manganese, vanadium, chromium or silicon. For every percentage of magnesium added to the composition, the strength indicator changes by 30 MPa.
Aluminum-manganese alloys
To increase corrosion resistance, the aluminum alloy is diluted with manganese. This component further increases the strength of the product and weldability. Components that can be added to such compositions are iron and silicon.
Alloys with aluminum, copper and silicon
The second name of this material is alcusin. Grades of aluminum with the addition of copper and silicon are used to produce parts for industrial equipment. Thanks to their high technical characteristics, they can withstand constant loads.
Aluminum-copper alloys
In terms of technical characteristics, mixtures of copper and aluminum can be compared with low-carbon steels. The main disadvantage of this material is its susceptibility to the development of corrosive processes. A protective coating is applied to the parts, which protects them from environmental factors. The composition of aluminum and copper is improved using alloying additives. They are manganese, iron, magnesium and silicon.
Aluminum-silicon alloys
Such mixtures are called silumin. Additionally, these alloys are improved with sodium and lithium. Most often, silumin is used for the manufacture of decorative products.
Alloys with aluminum, zinc and magnesium
Aluminum-based alloys, to which magnesium and zinc are added, are easy to process and have a high strength index. The characteristics of the material can be increased by heat treatment. The disadvantage of a mixture of three metals is low corrosion resistance. This drawback can be corrected with the help of a copper dopant.
Avial
These alloys include aluminum, magnesium and silicon. Distinctive features - high ductility, good resistance to corrosion processes.
Areas of application of aluminum alloys
Areas of application of aluminum and its alloys:
- Cutlery. Aluminum utensils, forks, spoons and containers for storing liquids are still popular.
- Food industry. This metal is used as a food additive. Its designation in the composition of products is E. It is a food additive used to color confectionery products or protect products from mold.
- Rocket science. Aluminum is used to make rocket propellant.
- Military industry. An acceptable price and low specific gravity have made this metal popular in the production of parts for small arms.
- Glassmaking. This material is used in the manufacture of mirrors. This is due to its high reflectivity.
- Jewelry. Aluminum jewelry used to be very popular. However, it was gradually replaced by silver and gold.
Due to its high electrical conductivity, this metal is used for the manufacture of wires and radio components. In terms of electrical conductivity, aluminum is second only to copper and silver.
We must not forget about the small specific gravity of the material. Aluminum is considered one of the lightest types of metal. Due to this, it is used to make housings for aircraft and cars. Delving deeper into this topic, we can say that the entire aircraft consists of at least 50% of this metal.
This metal is also found in the human body. If this component is missing, the processes of tissue growth and regeneration slow down. The person feels tired, muscle pain and increased drowsiness may appear. However, more often situations arise when this component is more than normal in the body. Because of this, a person becomes irritable and nervous.
In case of excess, it is necessary to abandon cosmetics with the addition of aluminum and medications containing it in the composition.
Aluminum.
Aluminum alloys. Aluminum bicycle frames. Mixtures with aluminum are common in various industries. This is due to the fact that this metal is among the top 5 most common in the world. In nature it is found in various ores.
In production, the weak performance of this metal is increased by adding other components. This way you can increase resistance to corrosion processes, strength, and melting point.
Source: https://metalloy.ru/splavy/alyuminievye
Types of aluminum alloys
Aluminum is a metal that is often thrown into the air, and is also used in the construction of ships, houses, and even used in the production of cars. This material is not distinguished by the highest strength and durability, and is even considered quite soft. But what is it about it that makes it considered the “metal of the future”?
A simple processing process, lightness and abundance are the main advantages of aluminum, and it is really useless to argue with them. Moreover, this metal conducts heat well and, when heated, does not emit harmful or toxic substances. The most important point is that by adding a minimal amount of another element, you can get a material with completely opposite properties.
Classification of aluminum alloys
Alloying is the process by which aluminum alloys are made. If we consider this topic in more detail, we can understand that this is not one, but several processes that complement each other. The essence of alloying is to introduce auxiliary elements into molten aluminum in the required quantity.
The quantity depends on the result you want to get in the end. It is also important to take into account that this metal already contains a certain proportion of iron and silicon. These substances have a negative effect on the resulting alloy - they will reduce ductility, corrosion resistance and electrical conductivity.
Aluminum alloys are classified in several ways. In particular, they are classified according to the type of alloying elements:
- containing intrametallics (lithium and copper, silicon and magnesium);
- containing additives (chrome, lithium, zinc, magnesium, etc.).
Taking into account the chosen method of processing that the substances will subsequently undergo, alloys are divided into:
- deformable aluminum alloys – without turning into liquid, the alloys acquire plasticity. They are easily pressed, forged, extruded and rolled. To achieve strength, alloys that are processed at a sufficiently high temperature, the rest are processed under pressure;
- Wrought alloys are cast aluminum alloys that are in a very liquid state so they can be poured into the desired shape. They are easy to cut, so you can get molding and shaped products.
According to the degree of strength, aluminum alloys are divided into:
- low-strength (up to 300 MPa);
- super-strong (from 480 MPa);
- medium-strength (from 300-480 MPa).
To easily and quickly distinguish aluminum alloy, each has its own number, which consists of numbers and letters.
The number indicates the grade of aluminum alloy. For example, at the beginning they put one or more letters that mean the composition. After them is written a serial number consisting of numbers.
At the end they also write a letter that shows the method of processing the alloy and its type at that moment.
For example, any alloy is designated as D16P. The letter “D” means duralumin – an alloy of magnesium, copper and aluminum; serial number – 16. The last letter “p” means that this alloy is semi-cold-hardened – those that have undergone pressure treatment.
The production of aluminum alloys in a foundry, as well as their application, differ depending on their grade and type. Each individual alloy is characterized by its own, rather specific set of physical and mechanical properties.
For example, among these properties there are those that significantly influence the further fate of the alloy, that is, where it will be used after the plant - at a construction site, at an airbase or in a workshop for the production of kitchen items.
Experts note the following properties - density, corrosion resistance, thermal conductivity, strength, ductility.
Aluminum bronzes are considered a separate category. These include alloys with the main alloying element - aluminum, based on copper. In this case, two-component alloys or alloys with a large number of components are most often used.
Source: https://zsm-m.ru/products/liteynoe-proizvodstvo/vidy-alyuminievykh-splavov/
What aluminum alloys are called silumins
Few people know about the existence of such an alloy as silumin, but most come across it in the form of various products. It is used to make water taps, dishes and many other metal objects. So what is this alloy?
Silumin is an alloy based on aluminum and silicon. The majority, namely about 90%, of the alloy is aluminum, the rest is silicon. The production of silumin is very similar to the production of duralumin, but the latter also contains copper, magnesium and manganese.
Silumin
The main difference between this alloy and conventional aluminum is that silumin has a higher level of strength.
Chemical properties
Despite the fact that this group includes alloys of aluminum and silicon, it should be noted that silumin can contain many other elements in small quantities. The composition of the alloy directly affects the characteristics of the finished products. The main condition for classifying an alloy as silumin is the percentage of silicon. It should be between 10% and 15%.
Due to the fact that aluminum makes up about 90%, the structure of silumin is very similar to the structure of aluminum. It is almost impossible to distinguish them with the naked eye.
The properties of silumin differ depending on the type of aluminum alloy. There are two types of metals in this group:
- normal silumins;
- wear-resistant.
The normal group has a silicon content of around 12%. The strength of alloys of this group is not at a high level, but they have other advantages. First of all, ease of processing and excellent casting properties. The absence of various impurities makes this type of silumin neutral to the effects of aggressive environments and various chemicals.
Microstructure of silumin
Wear-resistant alloys contain about 20% silicon. This composition gives silumin increased strength, significantly exceeding the strength of aluminum. But processing products made from this alloy is more complex and requires greater effort.
Characterizing the chemical properties of silumin, it should be noted that they practically do not differ from the properties of aluminum. They vary only slightly depending on the percentage of various additives. First of all, adding silicon to aluminum directly affects the physical properties.
Physical properties
An alloy such as silumin is often compared with stainless steel in its physical properties. But it is much lighter than steel, which is its main advantage.
Despite its low weight, the strength of silumin is not inferior to steel and other analogue metals. Like aluminum, this alloy does not corrode; this is facilitated by a protective film that is formed from oxide compounds.
Such a film is formed on the surface at the slightest damage through the interaction of oxygen and aluminum molecules.
The color of silumin is gray, when cut it is silvery, very much reminiscent of the color of aluminum.
Decorative elements made of silumin
The light weight of the alloy with high strength is possible due to the low density of the composition, which is significantly lower than that of steel. Considering the above advantages, the use of silumin today is preferable to the use of steel. Considering the relatively low cost of the alloy, silumin is used to produce cheap household appliances, which are often not inferior in reliability to expensive analogues.
Its advantage is also plasticity. This makes it suitable for casting complex shapes that require uniform metal distribution and a strong structure. Casting in this case requires less effort, which makes production more economical.
The melting point of silumin is about 670 degrees, which is much lower than the melting point of steel. This physical property also affects the reduction in the cost of metal products.
It should be noted that physical properties directly depend on the amount of impurities. These include magnesium and manganese, which are added purposefully. Or zinc, calcium and iron, which are simply not disposed of in production. Therefore, the quality of silumin may differ even with the same labeling - it depends on the production technology and the integrity of the manufacturer.
Physical properties also include increased wear resistance. Products made from this substance are resistant to mechanical stress and have a long service life.
Silumin engine block head
A disadvantage of the material is fragility. The products have an increased level of strength, but if this threshold is exceeded they may crack. They can be repaired using either epoxy glue or welding. But welding work should be carried out with care so as not to melt the product. Argon with solders is usually used for welding aluminum.
Area of application of silumin
Today, the scope of application of silumin is varied, but it is most often used in the production of cars and aircraft. Main areas of application:
- It has gained high popularity in the aircraft industry due to its combination of low weight and high strength, which is very important for lifting aircraft into the sky and saving fuel.
- Similar properties are desirable in automobile production. Thus, the weight of the car directly affects the driving characteristics of the car, maneuverability on the road and fuel consumption. In the field of mechanical engineering, the alloy is used to produce engine parts.
- Recently, silumin has gained particular popularity in the weapons industry, especially for the production of air rifles. Airsoft players prefer weapons made from this material due to its light weight, high strength and reliability, which, given the high cost of such rifles, is an irreplaceable quality.
- It is also used in the production of many household products, from pots and pans to faucets. Household products made from silumin are popular due to their low cost.
Cauldron made of silumin Candlestick made of silumin
Marking
Based on the variability of alloys, a special silumin marking was developed. Thanks to it, it is possible to quickly and accurately select a material with the desired properties, determine the composition, percentage of elements and physical properties.
Marking is based on a combination of alphabetic and digital designations. The letters indicate the components that make up the alloy, for example, A-aluminum, K-silicon, C-zinc. The order of the letter designations is determined based on the percentage of components, so the silumin brand always begins with the letter A.
The numbers indicate the percentage of each component except aluminum in the composition. For example, AK20 indicates the presence of 20% silicon and, accordingly, 80% aluminum.
It should be noted that labeling may vary depending on manufacturers and country of production. Therefore, when purchasing products with unclear markings, it is better to consult with the seller.
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Source: http://ooo-asteko.ru/kakie-splavy-alyuminiya-nazyvayut-siluminami/
Aluminum alloys and their applications
Rare metal rises into the air as often as aluminum and is used in the construction of houses, cars and ships. It would seem - not the strongest, not the most resistant, rather soft. What is it about aluminum that makes it called the “metal of the future”?
Aluminum undoubtedly has several advantages that are difficult to argue with:
— lightness; - prevalence - aluminum is the most common metal on planet Earth;
— ease of processing;
Aluminum also does not emit harmful substances when heated and conducts heat well. But the most important thing is to add a little to pure aluminum, just a few tenths of another element, and... voila! You get a material with diametrically opposite physical and chemical properties. Some aluminum-based alloys are so strong that at temperatures up to -200 degrees Celsius they are comparable to titanium and steel!
Preparation and classification of aluminum alloys
The process of producing aluminum alloys is called alloying. However, alloying is more likely not one, but several interrelated processes. Its essence lies in the fact that auxiliary (alloying) elements are introduced into molten aluminum in amounts from several tenths to several thousandths of a percent.
The proportion of excipients directly depends on the result that needs to be obtained. It is important to consider that aluminum usually already contains iron and silicon. Both elements have a negative effect on the quality of the future alloy: they reduce its resistance to corrosion, electrical conductivity and ductility.
Due to the fact that aluminum and aluminum alloys are used in strategically important areas, they are subject to mandatory state certification and labeling. In Russia, the quality of alloys is determined on the basis of two GOSTs: No. 4784-97 and No. 1583-93.
Aluminum alloys can be classified in several different ways. According to the type of auxiliary (alloying) elements, alloys are:
- with the addition of additives (individual elements - zinc, magnesium, manganese, chromium, silicon, lithium, etc.);
- with the addition of intrametallics (compounds of several metals - magnesium + silicon, copper + magnesium, lithium + magnesium, lithium + copper, etc.).
Depending on the chosen method of further metalworking, they are divided into:
- deformable aluminum alloys (the alloy does not turn into liquid, but simply becomes very plastic) - they are convenient to stamp, forge, roll, extrusion, pressing. To achieve greater strength, some of the alloys are processed at elevated temperatures (annealing, hardening and aging), while others are processed under pressure. The result is aluminum workpieces such as sheets, profiles, pipes, products of more complex shapes, etc.
- casting aluminum alloys (the alloy enters production in a very liquid state so that it can easily be poured into some form) - such alloys are easy to cut, they produce cast shaped (obtained under pressure) and molding products.
All aluminum-based alloys can also be divided according to strength into:
— super-strong (from 480 MPa); - medium-strength (from 300 - 480 MPa);
— low-strength (up to 300 MPa);
Alloys resistant to high temperatures and corrosion are classified separately.
To make products made from alloys easy to distinguish, each alloy is assigned its own number, consisting of letters and numbers. This number indicates the grade of aluminum alloy. A letter or several letters are placed at the beginning of the brand name; they indicate the composition of the alloy. Then comes the digital serial number of the alloy. The letter at the end shows how the alloy was processed and in what form it is currently in.
Let's look at the principle of marking using the example of alloy D16P. The first letter in the brand “D” means duralumin, that is, an alloy of aluminum with copper and magnesium. “16” is the serial number of the alloy. “P” - semi-hardened, that is, the alloy has been cold-worked by pressure to a strength value half of the maximum.
The production of aluminum alloys and their applications vary greatly depending on the type and brand. Each alloy has its own, very specific set of physical and mechanical properties. Among these properties there are those on which the further fate of the alloy depends - where it goes from the factory: to an airbase, to a construction site and to a kitchen utensils manufacturing workshop. These properties are the following: strength level, corrosion resistance, density, ductility, electrical and thermal conductivity.
Basic properties of various aluminum alloys
Let's look at the main aluminum-based alloys from the point of view of their acquired properties.
The alloy of copper and aluminum comes in several types - “pure”, in which the main active elements are Al and Cu, “copper-magnesium”, in which, in addition to copper and aluminum, magic occupies a certain proportion and “copper-manganese” with alloying with manganese. Such alloys are often also called duralumin; they are easy to cut and spot weld.
A characteristic feature of duralumin is that they use aluminum with admixtures of iron and silicon. As we have already said, usually the presence of these elements deteriorates the quality of the alloy, but this case is an exception. Iron, during repeated heat treatment of the alloy, increases its heat resistance, and silicon acts as a catalyst in the “aging” process of duralumin. In turn, magnesium and manganese as alloying elements make the alloy much stronger.
An alloy of aluminum and magnesium has different strength and ductility, depending on the amount of magnesium. The less magnesium, the lower the strength of the product made from such an alloy and the higher the resistance to corrosion.
An increase in magnesium content by 1% leads to an increase in strength up to 30,000 Pa. On average, alloys based on magnesium and aluminum contain up to 6% of the former.
Why not more? If there is too much magnesium in the alloy, a product made from it will quickly become covered with rust, and in addition, such products have an unstable structure, may crack, etc.
Heat treatment of magnesium alloys with aluminum is not carried out, since it is ineffective and does not give the necessary effect of increasing strength.
An alloy of aluminum with zinc and magnesium is considered the most durable of all aluminum alloys known today. Its strength is comparable to titanium! During heat treatment, most of the zinc is dissolved, which is what makes this alloy so strong.
True, it is impossible to use products made from such alloys in the electrical industry; they are not resistant to stress corrosion. You can slightly increase the corrosion resistance if you add copper to the composition, but the indicator will still remain unsatisfactory.
Aluminum-silicon alloy is the most common alloy in the foundry industry. Since silicon dissolves well in aluminum when heated, the resulting molten composition is excellently suitable for molding and shaped casting. Finished products are relatively easy to cut and have a high density.
An alloy of aluminum with iron, like alloys of aluminum with nickel, is practically never found in real life. Iron is added solely as an auxiliary element so that the casting alloy can easily come off the walls of the mold. Nickel, in turn, is best known in the production of magnets and is present as one of the elements in the aluminum-nickel-iron alloy.
An alloy of titanium and aluminum is also not found in its pure form and is used only to increase the strength of products. For the same purpose, welding of steel and aluminum alloys is carried out.
Source: https://promplace.ru/vidy-metallov-i-klassifikaciya-staty/splavy-aluminiya-1504.htm
Aluminum alloys: properties and choice
Aluminum alloy – an aluminum-based alloy is aluminum that [1]:
- contains one or more alloying elements, as well as some impurities;
- aluminum predominates by mass over each of the other chemical elements;
- aluminum content does not exceed 99.00%.
An alloying element is a metallic or non-metallic element that is controlled within certain upper and lower limits for the purpose of imparting certain special properties to the aluminum alloy [1].
An impurity is a metallic or non-metallic element that is present in an alloy, the minimum content of which is not controlled. In aluminum alloys, as a rule, the maximum impurity concentration is controlled [1].
Alloying in aluminum alloys
The most important alloying elements that are used to transform aluminum into alloys with special properties - both wrought and castable (of course, in different quantities) - are:
- silicon (Si),
- magnesium (Mg),
- manganese (Mn),
- copper (Cu) and
- zinc (Zn).
The effect, for example, of copper content in an aluminum alloy on its mechanical properties is shown in Figure 1.
Figure 1 - Effect of alloying an aluminum alloy with copper on mechanical properties [3]
Iron in aluminum alloys
Wrought aluminum alloys contain approximately 0.1 – 0.4% (by weight) iron (Fe). Iron is generally viewed as an undesirable impurity. Its content depends on the quality of the original ore (bauxite) and the electrolytic reduction technology. Sometimes iron alloying is used to obtain special properties of a material, for example, to make aluminum foil.
Modification of alloys
Other alloying elements often used in combination with the main alloying elements are bismuth (Bi), boron (B), chromium (Cr), lead (Pb), nickel (Ni), titanium (Ti) and zirconium (Zr). These elements are usually used in small quantities (up to 0.1% by weight, although B, Pb and Cr can make up up to 0.5%) to give them special properties, modify alloys for special purposes such as castability, machinability, heat resistance, corrosion resistance, strength, etc.
Two categories: cast and wrought
Two categories of aluminum alloys
Cast aluminum alloy is an aluminum alloy that is intended primarily for the production of castings.
Wrought aluminum alloy is an aluminum alloy that is intended primarily for the production of aluminum products by hot and/or cold forming.
Wrought alloys
Wrought aluminum alloys are first cast into ingots (round or rectangular), and then processed using various forming technologies - hot and cold - until they are given the desired shape:
- rolling - to produce sheets and foil;
- pressing - to produce profiles, pipes and rods;
- molding - to obtain more complex shapes from rolled or pressed semi-finished products;
- forging to obtain complex shapes with increased mechanical properties, as well as:
- drawing, stamping, upsetting, drawing, rolling, spreading, bending, etc.
Popular wrought aluminum alloys of the 6xxx series, which are used for the production of extruded aluminum profiles, are presented below in Figure 7.
Figure 7 – Main aluminum alloys of the 6xxx series
Casting alloys
Cast aluminum alloys in the molten state are poured directly into their final form by one of various methods such as sand casting, die casting or die casting. When casting, complex molds are used. These alloys often have a high silicon content to improve their castability.
These two categories of aluminum alloys have different classifications of alloying alloys: in general, the same alloying elements are added to them, but in different quantities.
The strength and other mechanical properties of aluminum alloys, both wrought and cast, are determined mainly by their chemical composition, i.e., the content of alloying elements in aluminum, as well as harmful impurities.
However, it is possible to change these properties to achieve their optimal combination by additional processing of the alloys - thermal or deformation, or both. As a result of this, the alloy changes its original mechanical properties and receives its final state, in which it is delivered to the customer.
Heat strengthening treatment is applied to both cast and wrought alloys. They are then called heat treatable alloys.
Two hardening mechanisms
Two classes of aluminum alloys:
- thermally hardenable
- strain-hardened (cold-hardened)
Thermally hardenable alloys
A heat-hardening alloy is an alloy that can be strengthened by appropriate heat treatment (Figures 2, 3 and 4).
Figure 2 – Quenching and aging hardening of aluminum alloys [2]
Figure 3 – Typical thermal hardening by aging [4]
Figure 4 – Effect of thermal hardening on the mechanical properties of alloy 7075 [4]
Cold-worked alloys
A strain-hardening alloy (“thermally non-hardening”, work hardening) is an alloy that is strengthened only by deformation treatment (Figures 5 and 6), and not by heat treatment.
Figure 5 - The influence of cold plastic processing - cold hardening - on the strength, hardness and ductility of aluminum alloys [2]
Figure 6 – Cold hardening curves (strain hardening)
of thermally non-hardening aluminum alloys [4]
Series and alloying systems
- All aluminum alloys - both wrought and cast - are divided into series according to the main alloying elements.
- Each series of aluminum alloys, wrought and cast, includes one, two or three different alloying systems.
- The alloying system may include only the main alloying element (shown below in bold) or additionally one or more alloying elements.
Wrought alloy series
- 2xxx – Al- Cu , Al- Cu -Mg, Al- Cu -Mg-Si, Al- Cu -Li
- 3xxx – Al- Mn
- 4xxx – Al- Si
- 5xxx – Al- Mg
- 6xxx – Al- Mg-Si
- 7xxx – Al- Zn , Al- Zn -Mg, Al- Zn -Mg-Cu
- 8xxx – Al-Fe, Al-Fe-Ni, Al-Li-Cu-Mg
Casting alloy series
- 2xx – Al- Cu , Al- Cu -Ni-Mg, Al- Cu -Si,
- 3xx – Al- Si -Cu, Al- Si -Cu-Mg, Al- Si -Mg
- 4xx – Al- Si
- 5xx – Al- Mg
- 7xx – Al- Zn
- 8xx – Al- Sn
strength of aluminum alloys
Unalloyed aluminum has a tensile strength of about 90 MPa. However, aluminum alloys are obtained by small additions of alloying elements such as copper, magnesium, manganese, silicon, zinc, and small amounts of some other elements.
Aluminum alloys are created in order to obtain aluminum with special properties, for example, with higher mechanical properties (Figure 8).
Figure 8 – strength of deformable aluminum alloys [2]
Alloy selection
When choosing an aluminum alloy as a structural material, the main factor is to ensure the strength of the structural element made from it. However, the structural strength of different types of elements is provided by different properties of the same structural material.
For example, the strength of a "thick" column will depend mainly on the yield strength of the metal, while the strength of a "thin" column will depend mainly on the elastic modulus of the material.
Since the yield strength of aluminum alloys is often comparable to the yield strength of ordinary structural steels, aluminum could easily compete with them for “thick” columns.
On the other hand, since the modulus of elasticity of aluminum and its alloys is only about a third of that of steels, aluminum can hardly compete with steels in “thin” columns.
Strength, however, is not the only performance characteristic of a structure or product. Additional factors such as corrosion resistance, ease of processing (compressibility or weldability), stiffness (modulus of elasticity), ductility (elongation), weight (density), fatigue strength, and cost must be taken into account to some extent when choosing the required construction material.
Economics of aluminum construction
Often the cost of the material is a critical factor. However, comparing aluminum alloys and steels based on cost per unit mass or volume can be misleading because they have different strengths, densities, and other properties.
If the cost of the material were the only factor and carbon steels could be used without a protective anti-corrosion coating, then only they would be used everywhere and always. However, when choosing a material, other factors are also taken into consideration, such as the cost of operation and maintenance over the life of the structure.
In addition, in some specific conditions the “rule” that an aluminum element is twice as light as a steel one is not always true. For example, an aluminum component can weigh significantly less if the thickness of the steel element needs to be increased to take into account its possible reduction from exposure to too aggressive corrosion over the entire service life.
If profiles with complex cross sections are required, as, for example, in facade enclosing structures, then in such cases, the cost of the steel element is much greater than the cost of its material.
The fact is that in order to manufacture this element from a steel billet, it must be mechanically processed, cold stamped or bent, and, perhaps, welding must be used.
At the same time, the cost of manufacturing an aluminum profile is only a small fraction of the cost of “raw” aluminum.
Due to the high cost of stainless steels, they are used only if the weight of the element or structure is not important, but appearance and weldability are important. Typically, when stainless steel is used instead of aluminum, there is often only one reason - the welding limitations of aluminum alloys.
Aluminum alloys according to Eurocode 9
Aluminum alloys offer design engineers a wide choice of materials. Each alloy has its own special characteristics that serve to provide specified properties. When corrosion resistance, high strength-to-weight ratio and ease of fabrication are essential design parameters, then aluminum alloys deserve serious consideration.
Tables 1 and 2 present wrought aluminum alloys that Eurocode 9 recommends and allows for use in buildings and structures (see more details here).
Table 1 - Thermally non-hardening aluminum alloys according to Eurocode 9
Table 2 - Thermally non-hardening aluminum alloys according to Eurocode 9
1. Guidance GAG Guidance Document 001 Terms and Definitions Edition 2009-01 March 20092. The welding of aluminum and its alloys / Gene Mathers – Woodhead Publishing Ltd, 20023. Aluminum and Aluminum Alloys / ed. Davis - ASM International, 1996
4. Aluminum and Aluminum Alloys – Subject Guide – ASM International, 2015
Source: https://aluminium-guide.ru/aluminievye-splavy-klassifikacija-primenenie-svojistva-kharakteristik/
Aluminum alloys and their applications
Aluminum is used for the production of products and alloys based on it.
Alloying is the process of introducing additional elements into the melt that improve the mechanical, physical and chemical properties of the base material. Alloying is a general concept of a number of technological procedures carried out at various stages of obtaining metal material with the aim of improving the quality of metallurgical products.
The introduction of various alloying elements into aluminum significantly changes its properties, and sometimes gives it new specific properties.
The strength of pure aluminum does not satisfy modern industrial needs, therefore, for the manufacture of any products intended for industry, not pure aluminum, but its alloys are used.
With various alloying, strength, hardness increase, heat resistance and other properties are acquired.
At the same time, undesirable changes also occur: electrical conductivity inevitably decreases, in many cases corrosion resistance deteriorates, and relative density almost always increases.
The exception is alloying with manganese, which not only does not reduce corrosion resistance, but even slightly increases it, and magnesium, which also increases corrosion resistance (if it is not more than 3%) and reduces the relative density, since it is lighter than aluminum.
Aluminum alloys
Aluminum alloys, according to the method of manufacturing products from them, are divided into two groups: 1) deformable (have high ductility when heated),
2) foundry (have good fluidity).
This division reflects the basic technological properties of alloys. To obtain these properties, different alloying elements are introduced into aluminum and in unequal quantities.
The raw materials for the production of alloys of both types are not only technically pure aluminum, but also double alloys of aluminum with silicon, which contain 10-13% Si, and differ slightly from each other in the amount of impurities of iron, calcium, titanium and manganese. The total content of impurities in them is 0.5-1.7%. These alloys are called silumins.
To obtain wrought alloys, mainly soluble alloying elements are introduced into aluminum in quantities not exceeding the limit of their solubility at high temperatures. When heated under pressure, deformable alloys must have a homogeneous solid solution structure, which provides the greatest ductility and the lowest strength.
This determines their good workability under pressure.
The main alloying elements in various wrought alloys are copper, magnesium, manganese and zinc; in addition, silicon, iron, nickel and some other elements are also introduced in relatively small quantities.
Duralumin - alloys of aluminum and copper
Typical hardenable alloys are duralumin - aluminum-copper alloys that contain permanent impurities of silicon and iron and can be alloyed with magnesium and manganese. The amount of copper in them is in the range of 2.2-7%.
Copper dissolves in aluminum in an amount of 0.5% at room temperature and 5.7% at the eutectic temperature of 548 C.
Heat treatment of duralumin consists of two stages. It is first heated above the limiting solubility line (usually to approximately 500 C). At this temperature, its structure is a homogeneous solid solution of copper in aluminum. By hardening, i.e. rapid cooling in water, this structure is fixed at room temperature. In this case, the solution becomes supersaturated. In this state, i.e. in the hardened state, duralumin is very soft and ductile.
The structure of hardened duralumin has little stability and even at room temperature changes spontaneously occur in it. These changes boil down to the fact that the atoms of excess copper are grouped in the solution, arranged in an order close to that characteristic of crystals of the chemical compound CuAl.
The chemical compound has not yet been formed, much less separated from the solid solution, but due to the uneven distribution of atoms in the crystal lattice of the solid solution, distortions occur in it, which lead to a significant increase in hardness and strength with a simultaneous decrease in the ductility of the alloy.
The process of changing the structure of a hardened alloy at room temperature is called natural aging.
Natural aging occurs especially intensively during the first few hours, but is completely completed, giving the alloy its maximum strength, after 4-6 days. If the alloy is heated to 100-150 C, then artificial aging will occur. In this case, the process occurs quickly, but less hardening occurs.
This is explained by the fact that at a higher temperature, the diffusion movements of copper atoms occur more easily, so the CuAl phase is completely formed and separated from the solid solution.
The strengthening effect of the resulting phase turns out to be less than the effect of distortion of the solid solution lattice that occurs during natural aging.
A comparison of the results of aging duralumin at different temperatures shows that maximum strengthening is achieved with natural aging for four days.
Aluminum alloys with manganese and magnesium
Among non-hardening aluminum alloys, alloys based on Al-Mn and Al-Mg have acquired the greatest importance.
Manganese and magnesium, like copper, have limited solubility in aluminum, which decreases with decreasing temperature. However, the hardening effect during their heat treatment is small. This is explained as follows.
During the crystallization process in the manufacture of alloys containing up to 1.9% Mn, excess manganese released from the solid solution would have to form with aluminum a chemical compound Al (MnFe) soluble in it, which is insoluble in aluminum.
Consequently, subsequent heating above the limiting solubility line does not ensure the formation of a homogeneous solid solution; the alloy remains heterogeneous, consisting of a solid solution and Al (MnFe) particles, and this leads to the impossibility of quenching and subsequent aging.
In the case of the Al-Mg system, the reason for the lack of hardening during heat treatment is different. With a magnesium content of up to 1.4%, hardening cannot occur, since within these limits it dissolves in aluminum at room temperature and no precipitation of excess phases occurs. With a higher magnesium content, hardening followed by chemical aging leads to the release of an excess phase - the chemical compound MgAl.
However, the properties of this compound are such that the processes preceding its isolation, and then the resulting inclusions, do not cause a noticeable strengthening effect. Despite this, introducing both manganese and magnesium into aluminum is beneficial. They increase its strength and corrosion resistance (with a magnesium content of no more than 3%). In addition, magnesium alloys are lighter than pure aluminum.
Other alloying elements
Also, to improve some of the characteristics of aluminum, the following are used as alloying elements:
Beryllium is added to reduce oxidation at elevated temperatures. Small additions of beryllium (0.01-0.05%) are used in aluminum casting alloys to improve fluidity in the production of internal combustion engine parts (pistons and cylinder heads).
Boron is introduced to increase electrical conductivity and as a refining additive. Boron is introduced into aluminum alloys used in nuclear energy (except for reactor parts), because it absorbs neutrons, preventing the spread of radiation. Boron is introduced in an average amount of 0.095-0.1%.
Bismuth. Metals with low melting points such as bismuth, lead, tin, cadmium are introduced into aluminum alloys to improve machinability. These elements form soft, fusible phases that contribute to chip brittleness and cutter lubrication.
Gallium is added in an amount of 0.01 - 0.1% to the alloys, from which consumable anodes are then made.
Iron. It is introduced in small quantities (>0.04%) in the production of wires to increase strength and improve creep characteristics. Iron also reduces adhesion to the walls of molds when casting in a chill mold.
Indium. An addition of 0.05 - 0.2% strengthens aluminum alloys during aging, especially with low copper content. Indium additives are used in aluminum-cadmium bearing alloys.
Cadmium. Approximately 0.3% cadmium is introduced to increase the strength and improve the corrosion properties of the alloys.
Calcium imparts plasticity. With a calcium content of 5%, the alloy has the effect of superplasticity.
Silicon is the most used additive in foundry alloys. In an amount of 0.5-4% it reduces the tendency to cracking. The combination of silicon and magnesium makes it possible to heat seal the alloy.
Tin improves cutting performance.
Titanium. The main task of titanium in alloys is to refine the grain in castings and ingots, which greatly increases the strength and uniformity of properties throughout the entire volume.
Application of aluminum alloys
Most aluminum alloys have high corrosion resistance in the natural atmosphere, sea water, solutions of many salts and chemicals, and in most foods. The latter property, combined with the fact that aluminum does not destroy vitamins, allows it to be widely used in the production of tableware. Aluminum alloy structures are often used in seawater.
Aluminum is used in large quantities in construction in the form of cladding panels, doors, window frames, and electrical cables. Aluminum alloys are not subject to severe corrosion over a long period of time when in contact with concrete, mortar, or plaster, especially if the structures are not frequently wet. Aluminum is also widely used in mechanical engineering, because...
has good physical qualities.
But the main industry that is currently simply unthinkable without the use of aluminum is, of course, aviation. It was in aviation that all the important characteristics of aluminum were most fully used
Other articles on similar topics
Source: https://TochMeh.ru/info/alum3.php
What aluminum alloys are called silumins - Metals, equipment, instructions
Few people know about the existence of such an alloy as silumin, but most come across it in the form of various products. It is used to make water taps, dishes and many other metal objects. So what is this alloy?
Silumin is an alloy based on aluminum and silicon. The majority, namely about 90%, of the alloy is aluminum, the rest is silicon. The production of silumin is very similar to the production of duralumin, but the latter also contains copper, magnesium and manganese.
Silumin
The main difference between this alloy and conventional aluminum is that silumin has a higher level of strength.
