The content of trace elements determines the properties of aluminum alloy plate

Iron and silicon

Iron in Al Cu Mg Ni Fe System forging aluminum alloy, silicon in Al Mg SI system Forging Aluminum and in Al Si system welding rod and Al Si casting alloy, are added as alloy elements. In other aluminum alloy, silicon and iron are common impurity elements, which have obvious influence on the properties of alloy. They mainly exist in FeCl3 and free silicon. When silicon is larger than iron, β - fesial3 (or fe2si2al9) phase is formed, while when iron is larger than silicon, α - fe2sial8 (or fe3si2al12) phase is formed. When the ratio of iron to silicon is not right, it will cause cracks in castings, and when the iron content in aluminum is too high, it will cause brittleness in castings.

Titanium and boron

Titanium is a common addition element in aluminum alloy. It is added in the form of Al Ti or Al Ti-B master alloy. Titanium and aluminum form TiAl2 phase, which becomes the non spontaneous core during crystallization, and plays the role of refining the casting structure and weld structure. The critical content of Ti in Al Ti alloy is about 0.15% when the inclusion reaction takes place. If there is boron, the reduction rate will be as low as 0.01%.

chromium

Chromium is a common additive element in Al Mg Si, Al mg Zn and Al Mg alloys. At 600 ℃, the solubility of chromium in aluminum is 0.8%, which is almost insoluble at room temperature.

Chromium forms (CrFe) AL7 and (CrMn) al12 intermetallic compounds in aluminum, which hinder the nucleation and growth of recrystallization, strengthen the alloy to a certain extent, improve the toughness and reduce the sensitivity of stress corrosion cracking. However, the quenching sensitivity was increased in the venue, which made the anodized film yellow.

The amount of chromium in aluminum alloy is less than 0.35%, and decreases with the increase of transition elements.