Al-Li合金回归再时效的微观相场模拟

Microscopic Phase Field Simulation of The Retrogression-Reaging (Rra) Treatment on Al-Li Alloys

基于离散格点形式的微观相场动力学扩散方程,以Al-11.7Li(原子分数,%)合金为对象,模拟了Al-Li合金时效,经历了3种不同程度的回归再时效过程。这3种回归为:完全回归(δ′相全部溶解)、不完全回归(δ′相未全部溶解,少量存在)以及部分回归(δ′相部分溶解)。结果表明:对于该浓度合金,完全回归再时效获得的组织形貌与直接时效的相当;而不完全回归再时效得到的颗粒密度大于前两者,颗粒尺寸更加细化,分布更均匀,弥散度也高,不完全回归再时效能够有效地改善Al-Li合金的微观组织;部分回归再时效获得的δ′相粗大且数量少。

Based on microscopic phase field dynamic diffusion equations with the discrete format, the aging heat treatment and three different retrogression-reaging（RRA） heat treatments to an Al-11.7at.%Li alloy were studied using computer simulation. Firstly, the aging heat treatment was carried out at 190 ℃ to the alloy, then the retrogression was preformed in three different time steps at 360 ℃, among things for the retrogression in 33 200 time steps there was full dissolution of δ＇ （Al3Li） and in 300 000 time steps there was only partial δ＇ in existence and in 200 000 time steps there was partial dissolution of δ＇. Follow on, the reaging heat treatments were conducted 190 ℃. The morphologies of precipitates δ＇ phase were analyzed in qualitatively and quantitatively for above four simulations. The results shows that by RRA with full dissolution of δ＇ the microstructure is the same as that by aging; by RRA with only partial δ＇ in existence the optimum morphologies, i.e time δ＇ particle size and high particle concentration can be obtained; while the RRA with partial dissolution of δ＇ leads to a few and larger particles.