Where aluminum alloy castings can be heat treated, the heat treatment process can be divided into the following four categories:
1. Annealing treatment: aluminum alloy castings heated to high temperatures, is about 300 ℃ or so commonly, heat preservation, after a certain amount of time with the process known as annealing furnace cooling to room temperature.In the process of annealing, the solid solution is decomposed and the second phase particle is aggregated, which can eliminate the internal stress of the casting, stabilize the casting size, reduce the deformation and increase the plasticity of the casting.
2. Solid solution treatment: the temperature of the heat of the casting to as high as possible, close to the eutectic melting point, the temperature stay long enough, and then rapidly cooling, intensify group yuan maximum dissolved, the preserved by fixed high temperature to room temperature, the process is referred to as a solid solution treatment.Solid solution treatment can improve the strength and plasticity of casting and improve the corrosion resistance of alloy.
3. Aging process: the casting after solid solution treatment is heated to a certain temperature, and the casting is discharged after a certain time of heat preservation. The process of slowly cooling to room temperature in the air is called aging process.If the aging strengthening is carried out at room temperature, it is called natural aging. If the aging strengthening is carried out after a period of time when the temperature is higher than room temperature and the temperature is kept at room temperature, it is called artificial aging.The time-effect treatment is a spontaneous process of decomposition of supersaturated solid solution, so that the matrix of the alloy matrix can be restored to a relatively stable state.
4. Hot and cold cycle process: casting, treated by hot and cold cycle due to multiple heating and cooling of solid lattice contraction and expansion, make each phase of the lattice happened a little displacement, the second phase particle in a more stable state, thus improve the casting dimension stability, is suitable for manufacturing of precision parts.