Heat treatment of aluminum alloy die castings is to control the heating speed to the corresponding temperature, and then keep it warm for a certain period of time and then cool it at a certain rate. This can change the structure of the alloy, improve the mechanical properties of aluminum alloy die castings, enhance corrosion resistance, and improve processing performance and stability. What are the heat treatment technology processes?
1. Aging process
After quenching, the strength and hardness of aluminum alloy die castings will be significantly improved after standing for a period of time, while the plasticity will be significantly reduced. The phenomenon that the strength and hardness of aluminum alloy die castings after quenching increase significantly with time is called aging. Aging can occur at room temperature, called natural aging, or it can occur in a certain temperature range above room temperature, called artificial aging.
2. Strengthening principle of aluminum alloy
When aluminum alloy die castings are quenched and heated, vacancies are formed in the alloy. During quenching, due to rapid cooling, these vacancies have no time to move out and are "fixed" in the crystal. Most of these vacancies in the supersaturated solid solution are combined with solute atoms. Since the supersaturated solid solution is in an unstable state, it will inevitably change to an equilibrium state. The existence of vacancies accelerates the diffusion rate of solute atoms, thereby accelerating the segregation of solute atoms.
The size and number of hardened zones of aluminum alloy die castings depend on the quenching temperature and the quenching cooling rate. The higher the quenching temperature, the greater the vacancy concentration, the greater the number of hardened zones, and the smaller the size of the hardened zones. The greater the quenching cooling rate, the more vacancies fixed in the solid solution, which is conducive to increasing the number of hardened zones of aluminum alloy die castings and reducing the size of the hardened zones.
