Aluminum alloys can be divided into two categories: cast aluminum alloys and deformed aluminum alloys according to their composition and process properties. Deformed aluminum alloys are divided into four categories according to their performance and process performance: rust-proof aluminum, hard aluminum, super-hard aluminum and forged aluminum.
1. Anti-Rust Aluminum
The main alloying elements of rust-proof aluminum are manganese and magnesium, which belong to Al-Mn and Al-Mg system alloys. This kind of aluminum alloy belongs to the aluminum alloy that cannot be strengthened in time. After forging and annealing, it is a single-phase solid solution with high corrosion resistance and good plasticity. Manganese can improve the strength of aluminum alloy in aluminum through solid solution strengthening, but its main function is to improve the corrosion resistance of aluminum alloy. The second phase Mnal6 in the Al-Mn system alloy is close to the chemical properties of aluminum, so the manganese alloy has good corrosion resistance. Magnesium has less corrosion resistance damage to aluminum alloys and has good solid solution strengthening effect. Anti-rust aluminum has strong pressure processing ability, and can be processed by cold pressing to produce processing strengthening. It also welds well and cuts poorly (because it’s so soft). Anti-rust aluminum is used to manufacture corrosion-resistant, low-stress components, such as oil pipes, fuel tanks, rivets, etc.
Duralumin is basically an AU-Cu-Mg alloy with a small amount of manganese added to copper and magnesium. In addition to the solid solution strengthening effect, strengthening stages such as CuA12 (one phase) and Al2CuMg (S phase) are also formed. The addition of manganese is mainly to improve the corrosion resistance of the alloy, and also has a certain solid solution strengthening effect, but the precipitation tendency of manganese is small, so it does not participate in the timely process. All kinds of duralumin can be strengthened in time; the higher the content of copper and magnesium in the alloy, the more significant the effect of timely strengthening, the higher the strength, but the lower the plasticity and corrosion resistance. According to the degree of alloying, mechanical properties and process properties of the alloy, duralumin can be divided into spliced duralumin (2A01, 2A10), medium-strength duralumin (2Al1), separated hard duralumin (2A12, 2A06), heat-resistant duralumin (2A02) )Wait. Duralumin is the most widely used deformed aluminum alloy in the aviation industry, with strong hardening ability, and the strength can reach 500mpa after heat treatment. It is used to manufacture various load-bearing components in aircraft. Duralumin has poor corrosion resistance, especially in seawater. This is because it contains higher steel, and the electrode potential of copper solid solutions and compounds is more likely to cause intergranular corrosion than grain boundaries.
3. Super Hard Aluminum
Super hard aluminum is mainly Al-Cu-Mg-Zn system, such as 7A04 and so on. In addition to one phase and S phase, there are MgZn2 (one phase) and Al2Mg3Zn3 (T phase). Room temperature strength after quenching and aging treatment. It can exceed 600mpa and is a deformed aluminum alloy with strength. The disadvantage of this alloy is poor fatigue resistance, sensitivity to stress concentration, obvious stress corrosion tendency, and lower heat resistance than duralumin.
4. Forged Aluminum
Wrought aluminum belongs to Al-Mg-Si-Cu system and Al-Cu-Mg-Ni-Fe system alloy. Although there are many kinds of alloying elements in this aluminum alloy, the content of each element is very small, so it has good thermoplasticity. It is suitable for manufacturing various aviation forgings, especially large Aluminum forgings with complex shapes. Compounds such as Mg2Si, Al2Cumg, and Cual2 can be formed in the alloy. When human iron and nickel are added, the service temperature of the alloy can be increased, so it is called heat-resistant forged aluminum alloy. Commonly used wrought aluminum alloys include 6A02.2A50.2B50 and 2A14. Its supply state is generally quenched and artificially aged. For aluminum alloys that need to work at the separation temperature, a small amount of transition elements manganese, chromium, germanium, and titanium are usually added to dissolve in the matrix, which can greatly increase the recrystallization temperature. When the diffused second phase precipitates, it can effectively prevent recrystallization. Crystallization process and grain growth.
The recrystallization temperature is also an index reflecting heat resistance. Excessive content of alloying elements in the deformed aluminum alloy will seriously reduce the process plasticity and corrosion resistance of the alloy, and even make the pressure processing of the alloy difficult. Therefore, w(Cu) in deformed aluminum alloys generally does not exceed 5%, w(Mg) does not exceed 2.5%-5%, w(Zn) 3%-8%, and w(Si) 0.5%-1.2%. Elements such as iron and silicon are harmful impurities in deformed aluminum alloys. Most wrought aluminum alloys have good forgeability and can be used to produce forgings of various shapes and types. Aluminum satin pieces can be produced by existing forging methods, including free forging. Die forging. Xu Forging. Drum forging. Roller pressure. rotational pressure. Ring rolling and extrusion, etc. The flow stress of aluminum alloys varies significantly with composition, with each alloy having a flow stress value of about twice the value (ie, the required forging load differs by about two times); some low-strength aluminum or aluminum alloys, such as 1100 (equivalent to industrial pure Aluminum 1200) and 6A02, its flow stress is lower than that of carbon steel. The flow stress of high-strength aluminum alloys such as 7075 (LC4) and 7049 (LC6) is significantly higher than that of carbon steel.
Other aluminum alloys, such as 2219 (LY16), have flow stresses very similar to carbon steel. Aluminum alloys, as an alloy, can generally be considered more difficult to forge than carbon steel and many alloyed steels, but compared to nickel or cobalt alloys and titanium alloys, aluminum alloys are significantly easier to forge, especially when isothermal die forging techniques are employed. Deformed aluminum alloys can be divided into three categories according to process plasticity and mechanical properties. are of low intensity. High plasticity alloys include: 6A02, 3A21, 5A02, 5A03, 5A05 and industrial pure aluminum; medium strength and plasticity alloys include: 2A14, 2B50, 2A70, 2A80, 2A02, 2A06, 2A11, 2A16, 2A17, 5A06, etc.; Belongs to high strength. Low plasticity alloys include 2A14, 2A12, 7A04, etc. The figure shows the forgeability comparison of 10 representative aluminum alloys in aluminum alloy forging production.
The relative forgeability is based on the deformation string produced by each absorbing unit energy pier of 10 alloys in their respective forging temperature ranges. At the same time, it also takes into account the difficulty of meeting specific deformation requirements and the tendency to crack. The forgeability of various aluminum alloys increases with temperature, but the effect of temperature on various alloys is different. For example, the forgeability of 4032 alloys with high silicon content is very sensitive to temperature changes, while alloys such as high-strength Al-Zn-Mg-Cu series 7075 are least affected by temperature. The fundamental reason is that the types and contents of alloying elements in various alloys are different, which strengthens the properties of the phases. The quantity and distribution characteristics are also quite different, seriously affecting the plasticity and resistance to deformation of the aluminum alloy.
Some wrought aluminum alloys, such as 1100 and 3003 (LF21), are far from the alloys listed in the figure, but these alloys have limited application in forging production because they cannot be strengthened by heat treatment. Another characteristic of aluminum alloys related to their forgeability is poor flow. The so-called fluidity refers to the ability of the alloy to fill the cavity of the forging die under the action of external force. It mainly depends on the deformation resistance of the alloy and the external friction factor. The smaller the deformation resistance and the external friction factor, the better the fluidity. At the forging temperature, the deformation resistance of high-strength aluminum alloys is greater than that of steel, and the external friction factor is large, so the fluidity of aluminum alloys is poor.
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