ter quenching, the strength and hardness of automobile aluminum alloy increase significantly with the extension of time, which is called aging, also known as aging hardening of automobile aluminum alloy. This is one of the important ways to enhance the strength of automobile aluminum alloy.
According to the definition, the premise of aging hardening of automobile aluminum alloy is to get saturated single-phase structure by quenching. In a fast-hardening solution, not only the solute atoms are supersaturated, but also the vacancy (defect) is supersaturated, that is, in a double supersaturated state. Take aluminum -4% copper alloy as an example. After being treated by the solid solution, the chemical composition of supersaturated Alpha solid solution is the chemical composition of the alloy, that is, the content of steel in the solid solution is 4%.
As can be seen from the al-Cu phase diagram, at the equilibrium state of room temperature, the copper content in alpha solid solution is only 0.5%, so 3.5% Cu is in the supersaturated state and the solid solution is in the alpha phase. When the temperature is close to the melting point of pure aluminum, the vacancy concentration is close to 10-3 orders of magnitude, while at normal temperature, the vacancy concentration is 10-11 orders of magnitude, the difference between the two is 10-8 orders of magnitude. Studies show that; The higher the temperature and the higher the degree of supersaturation, the greater the effect of aging.
Therefore, the selection principle of solution temperature is to increase the solution temperature as much as possible without ablating the alloy.
The aging process of al - Cu alloy will take place at room temperature or certain temperature after solid solution treatment. This process is essentially the precipitation of Al2Cu in the second phase of supersaturated solid solution. This process is accomplished by formation and growth, which is a diffused solid phase transition. The order is: A through G. The area of P.
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