3 characteristics of aluminum alloy heat treatment
The principle of aluminum die casting heat treatment is to control the heating rate at a; heating and accelerated cooling. Thereby, the corrosion resistance of the aluminum alloy is improved, the processing ability is improved
1. Aluminum alloy heat treatment
The principle of aluminum die casting heat treatment is to control the heating rate at a; heating and accelerated cooling. Thereby, the corrosion resistance of the aluminum alloy is improved, the processing ability is improved, and dimensional stability is obtained.
2. Characteristics of aluminum alloy heat treatment
It is well known that steel with high carbon content can obtain higher hardness after quenching, but its ductility is very low. However, after the aluminum alloy is quenched, the strength and hardness of the aluminum alloy do not increase immediately. As for plasticity, it is not decreasing but increasing. But this quenched alloy, placed for a period of time (such as 4-6 days and nights), the strength and hardness will increase, and the plasticity will decrease. The phenomenon that the strength and hardness of aluminum alloys increase significantly with time after quenching is called aging. Aging can occur at room temperature and is called natural aging. Or it occurs in a temperature range higher than room temperature (such as 100 to 200 ℃), which is called artificial aging.
3. The principle of aging strengthening of aluminum alloy
Age hardening of aluminum alloys is a complex process. This depends not only on the composition of the alloy and the aging process, but also on the defects, especially the number and distribution of vacancies and dislocations, due to shrinkage of the alloy during production. The current age hardening is the result of the segregation of solute atoms to form a hardened zone.
When an aluminum alloy is quenched and heated, vacancies form in the alloy. These vacancies are too late to be removed due to rapid cooldown; fixed; in crystals. The openings of these supersaturated solid solutions bond with solute atoms. Supersaturated solid solutions are in an unstable state and transition to an equilibrium state. It accelerates the diffusion rate of the solute atoms and thus the separation of the solute atoms.
The size and number of hardened zones depend on the quench temperature and the quench cooling rate. The higher the quenching temperature, the more concentrated the vacancies, the greater the number of hardened zones, and the smaller the size. The greater the quench cooling rate, the more vacancies, which is beneficial to increase the number of hardened zones and reduce the size of hardened zones.
One of the characteristics of precipitation hardening alloys is that the equilibrium solid solubility changes with temperature, and the solid solubility increases with increasing temperature. Most aluminum alloys meet this criteria.