Four main introduction of heat treatment technology for aluminum alloy die casting: 1. Annealing treatment. 2. Solution treatment. 3. Aging treatment. 4. Cold and heat cycle treatment.
First, annealing treatment.
The process of heating aluminum alloy castings to a higher temperature is generally about 300 ℃, after holding for a certain time, the process of cooling to room temperature with the furnace is called annealing. In the annealing process, the solid solution decomposes and the second phase particles gather, which can eliminate the internal stress of the casting, stabilize the size of the casting, reduce the deformation and increase the plasticity of the casting.
Second, solution treatment.
The casting is heated to the highest temperature as possible, close to the melting point of the eutectic, and kept for a long time at this temperature, and then cooled quickly to make the reinforcement component dissolve to a greater extent. This high temperature state is fixed to room temperature, which is called solution treatment. Solid solution treatment can improve the strength and plasticity of castings and improve the corrosion resistance of the alloy.
Third, time limit treatment.
The process of heating the solid solution treated casting to a certain temperature, leaving the furnace after holding for a certain time, cooling slowly to room temperature in the air is called aging. If aging strengthening is performed at room temperature, it is called natural aging, if aging strengthening is performed after being higher than room temperature and kept for a period of time, it is called artificial aging. The aging treatment is a spontaneous process of supersaturated solid solution decomposition, which makes the lattice of alloy matrix return to a relatively stable state.
Fourth: cold and heat cycle treatment.
The lattice shrinkage and expansion of solid solution are caused by heating and cooling for many times, which makes the lattice of each phase shift a little, so that the second phase particle is in a more stable state, thus improving the stability of casting size and suitable for the manufacture of precision parts.