Purpose of heat treatment of aluminum alloy castings

Purpose of heat treatment of aluminum alloy castings

The purpose of heat treatment of aluminum alloy castings is to improve mechanical properties and corrosion resistance, stabilize dimensions, and improve machining properties such as machining and welding. Because the mechanical properties of many as cast aluminum alloys can not meet the service requirements, except for ZL102 of Al Si system, ZL302 of Al Mg system and ZL401 of Al Zn system, the mechanical properties and other service properties of castings should be further improved by heat treatment, including the following aspects:

1) Eliminate the internal stress caused by uneven cooling rate during crystallization and solidification due to casting structure (such as uneven wall thickness and large thickness at the joint);

2) Improve the mechanical strength and hardness of the alloy, improve the metallographic structure, and ensure that the alloy has certain plasticity, machinability and welding performance;

3) Stabilize the structure and size of the casting, prevent and eliminate the volume change caused by high temperature phase transformation;

4) Eliminate intergranular and compositional segregation and homogenize the structure.