When the aluminum-copper alloy is rich in aluminum portion 548, the large solubility of copper in aluminum is 5.65%, and when the temperature is lowered to 302, the solubility of copper is 0.45%. Copper is an important alloying element (analysis of aluminum alloy elements), and it has a certain solid solution strengthening effect. In addition, CuAl2 precipitated by aging has obvious aging strengthening effect. The copper content in aluminum alloy is usually 2.5%~5%, and the strengthening effect is good when the copper content is 4%~6.8%, so the copper content of most hard aluminum alloys is in this range.
The aluminum-copper alloy may contain less elements such as silicon, magnesium, manganese, chromium, zinc, and iron.
When the aluminum-rich portion of the Al-Si alloy is at a eutectic temperature of 577, the large solubility of silicon in the solid solution is 1.65%. Although the solubility decreases with decreasing temperature, such alloys are generally not heat treatable. Aluminum-silicon alloys have excellent casting properties and corrosion resistance.
If magnesium and silicon are simultaneously added to aluminum to form an aluminum-magnesium-silicon alloy, the strengthening phase is MgSi. The mass ratio of magnesium to silicon is 1.73:1. When the Al-Mg-Si alloy composition is designed, the contents of magnesium and silicon are arranged in this ratio on the substrate. In some Al-Mg-Si alloys, in order to increase the strength, an appropriate amount of copper is added, and an appropriate amount of chromium is added to offset the adverse effect of copper on corrosion resistance.
The equilibrium phase diagram of the Al-Mg2Si alloy alloy is rich in aluminum. The bulk solubility of Mg2Si in aluminum is 1.85%, and the deceleration is small as the temperature decreases.
Among the deformed aluminum alloys, silicon is added to aluminum alone and is limited to solder materials, and silicon has a certain strengthening effect when added to aluminum.
The equilibrium phase diagram of the Al-Mg alloy is rich in aluminum. Although the solubility curve indicates that the solubility of magnesium in aluminum is greatly reduced with temperature, in most industrially deformed aluminum alloys, the content of magnesium is less than 6%. The silicon content is also low, and these alloys are not heat-treated, but have good weldability, good corrosion resistance, and analysis of medium-strength aluminum alloy elements.
The strengthening of magnesium by aluminum is obvious. For every 1% increase of magnesium, the tensile strength is about 34 MPa. If less than 1% manganese is added, it may supplement the strengthening. Therefore, after adding manganese, the magnesium content can be lowered, and the hot cracking tendency can be reduced. In addition, manganese can uniformly precipitate the Mg5Al8 compound to improve the corrosion resistance and the welding performance.
In the equilibrium phase diagram of the Al-Mn alloy system, at the eutectic temperature of 658, the large 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 of zui. The Al-Mn alloy is a non-age hardening alloy, that is, it cannot be heat-treated.
Al-Zn alloy equilibrium phase diagram The solubility of zinc in aluminum in the aluminum-rich fraction 275 was 31.6%, while at 125 ° the solubility decreased to 5.6% aluminum alloy elemental analysis.
Zinc is added to aluminum alone. Under the deformation condition, the strength of the aluminum alloy is very limited, and there is a tendency of stress corrosion cracking, which limits its application.
Simultaneous addition of zinc and magnesium in aluminum forms a strengthening phase 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 yield strength can be significantly increased. The content of magnesium exceeds that of the superhard aluminum alloy required to form the Mg/Zn2 phase. When the ratio of zinc to magnesium is controlled at about 2.7, the stress corrosion cracking resistance is large.