失稳区Al-Li合金回归机制的计算机研究

Retrogression Mechanism Simulation of Al-Li Alloys in Destabilized Area

基于离散格点形式的微扩散方程 ,对失稳区Al Li合金在回归过程中Al3Li(δ′)相溶解做原子层面计算机模拟 ,分析析出相在回归过程中原子图像、序参数的演化 ,进而探讨Al Li合金的回归机制。探明在失稳区Al Li合金的回归过程有序相演化序列为 :化学计量比δ′相→非化学计量比有序相→无序基体。失稳区合金的回归过程为“小范围的成分回落” ,而时效过程为“大范围的成分起伏” ,因此 ,在失稳区合金回归过程并非时效过程的逆过程。

The dissolution process of L 12 ordered (Al 3Li) precipitations (δ′) in a disorde red matrix during retrogression heat treatment of Al-Li alloy in destabilized a r ea is investigated on atomic scale by using computer simulations based on micros copic diffusion equations (Langevin Equation) with the discrete format. The ato m ic pictures of evolutions and order parameter profiles with time are analyzed, a nd the retrogression mechanism of Al-Li alloy is described. In the course of r et rogression, it is proved that the evolution of δ′ phase in a disordered ma trix is in the order of stoicheometric δ′ phase→ nonstoicheometric ordered pha se → disordered matrix. The retrogression of alloys at destabilized area is composi t ional decline in a limited scope, but the phase precipitation at this area is co mpositional fluctuation in an extensive range, the retrogression is obviously no t the counter process of the phase precipitation.