1. Effect of alloying elements
When aluminum-copper alloy is rich in aluminum for some 548, the greater solubility of copper in aluminum is 5.65%, and when the temperature drops to 302, the solubility of copper is 0.45%. Copper is an important alloying element and has a certain solid solution strengthening effect. In addition, the time-dependent CuAl2 has a significant age strengthening effect. The copper content in aluminum alloys is generally between 2.5% and 5%, and the strengthening effect is better when the copper content is between 4% and 6.8%. Therefore, the copper content of some hard aluminum alloys is at this scale.
Aluminum-copper alloys can be enriched with less silicon, magnesium, manganese, chromium, zinc, iron and other elements.
Some Al-Si alloys are rich in aluminum. At a eutectic temperature of 577, the greater solubility of silicon in solid solution is 1.65%. Although the solubility decreases as the temperature decreases, such alloys are generally not heat treatable. Aluminum-silicon alloys have excellent forging and corrosion resistance.
If magnesium and silicon participate in aluminum to form an aluminum-magnesium-silicon-based alloy, the strengthening phase is MgSi. The mass ratio of magnesium to silicon is 1.73:1. When the composition of the Al-Mg-Si alloy is designed, the content of magnesium and silicon is provided on the substrate in this proportion. Some Al-Mg-Si alloys, in order to improve the strength, participate in appropriate copper and participate in appropriate chromium to offset the influence of copper on the anti-corrosive helium.
Al-Mg2Si Alloy Alloy Equilibrium Phase Diagram Aluminum-rich Some Mg2Si has a large solubility of 1.85% in aluminum and a small deceleration with decreasing temperature.
Among the deformed aluminum alloys, silicon alone is only limited to welding materials in aluminum, and silicon also has a certain strengthening effect in aluminum.
The equilibrium phase diagram of Al-Mg alloy is rich in aluminum. Although the solubility curve indicates that the solubility of magnesium in aluminum is greatly reduced with the decrease of temperature, in some industrial deformed aluminum alloys, the content of magnesium is less than 6%. The silicon content is also low, and such alloys are not heat-treated, but have good weldability, corrosion resistance, and moderate strength.
The strengthening of magnesium to aluminum is remarkable. For every 1% increase in magnesium, the tensile strength is about 34 MPa. If you participate in manganese below 1%, you can make up for the strengthening effect. Therefore, after adding manganese, the magnesium content can be lowered, and the thermal cracking tendency can be lowered together, and manganese can also uniformly precipitate the Mg5Al8 compound, thereby improving the corrosion resistance and the welding function.
The equilibrium phase diagram of the Al-Mn alloy system is somewhat at a eutectic temperature of 658, and the greater solubility of manganese in the solid solution is 1.82%. The strength of the alloy increases with increasing solubility. When the manganese content is 0.8%, the elongation reaches a large value. The Al-Mn alloy is a right-time hardening alloy, that is, it is not heat-treated.
Manganese can hinder the recrystallization process of aluminum alloys, improve the recrystallization temperature, and refine the recrystallized grains remarkably. The refinement of the recrystallized grains is primarily due to the effect of the diffusion of the MnAl6 compound on the growth of recrystallized grains. Another effect of MnAl6 is to dissolve the impurity iron to form (Fe, Mn)Al6, reducing the harmful effects of iron.
Manganese is an important element of aluminum alloy. It can participate in the formation of Al-Mn binary alloys alone, and more often participates in other alloying elements. Therefore, most of the aluminum alloys are rich in manganese.
The equilibrium phase diagram of the Al-Zn alloy is rich in aluminum. At some 275, the solubility of zinc in aluminum is 31.6%, while at 125, the solubility decreases to 5.6%.
Zinc alone participates in aluminum, and the improvement of the strength of aluminum alloy under deformation conditions is very limited, and there is a stress corrosion cracking and tendency together, thus constraining its application.
Participating in zinc and magnesium together in aluminum constitutes a strengthening phase of Mg/Zn2, which has a significant strengthening effect on the alloy. When the Mg/Zn2 content is increased from 0.5% to 12%, the tensile strength and the yield strength are remarkably increased. The content of magnesium exceeds that of the superhard aluminum alloy required to form the Mg/Zn2 phase. When the proportion of zinc and magnesium is manipulated at 2.7, the stress corrosion cracking resistance is large.
For example, the Al-Zn-Mg-Cu alloy is formed on the basis of Al-Zn-Mg, and the base strengthening effect is larger among all aluminum alloys. It is also an important aluminum alloy material in the aerospace, aviation industry and power industry. .
2. The influence of trace elements
Iron and silicon
In the Al-Cu-Mg-Ni-Fe system forging aluminum alloy, silicon is added as an alloying element in Al-Mg-Si-based forged aluminum and in Al-Si-based welding rod and aluminum-silicon forged alloy. Among the aluminum alloys, silicon and iron are common impurity elements and have a significant effect on the function of the alloy. They are primarily present in FeCl3 and free silicon. When silicon is larger than iron, it constitutes a β-FeSiAl3 (or Fe2Si2Al9) phase, and when iron is larger than silicon, it constitutes α-Fe2SiAl8 (or Fe3Si2Al12). When the iron and silicon share is improper, it will cause cracks in the casting. If the iron content in the cast aluminum is too high, the casting will be brittle.
Titanium and boron
Titanium is an additive element commonly used in aluminum alloys and is attended by Al-Ti or Al-Ti-B center alloys. Titanium and aluminum form the TiAl2 phase, which becomes the non-conscious center of crystallization, which serves to refine the forging arrangement and the weld arrangement. When the Al-Ti alloy is subjected to a package reaction, the critical content of titanium is about 0.15%, and if boron is present, the deceleration is as small as 0.01%.
An additive element which is more common in chromium in Al-Mg-Si system, Al-Mg-Zn system, and Al-Mg alloy. At 600 ° C, the solubility of chromium in aluminum is 0.8%, and it is substantially insoluble at room temperature.
Chromium forms intermetallic compounds such as (CrFe)Al7 and (CrMn)Al12 in aluminum, which prevents the nucleation and growth process of recrystallization, has a certain strengthening effect on the alloy, and improves the alloy resistance and the stress corrosion cracking sensitivity. . However, the site increased the quenching sensitivity and made the anodized film yellow.
The increase in chromium in aluminum alloys generally does not exceed 0.35% and decreases with the increase of transition elements in the alloy.