Stress/strain aging mechanisms in Al alloys from first principles

铝合金应力/应变时效机制的第一性原理研究(英文)

First-principles based calculations were carried out to explore the possible mechanisms of stress/strain aging in Al alloys. Potential effects of temperature and external stress/strain were evaluated on the solvus boundary of Al3Se in Al-Sc alloy, and the interface energy of Al/θ＂ in Al-Cu alloys. Results show that applying tensile strain/stress during conventional aging can significantly decrease the solubility entropy, by red-shifting the phonon DOS at high states. The resulted solvus boundary would shift up on the phase diagram, suggesting a reduced solubility limit and an increased maximum possible precipitation volume of AlaSc in Al-Sc alloy. Moreover, the applied strain/stress has different impacts on the formation energies of different orientated Al/θ＂ interfaces in Al-Cu alloys, which can be further exaggerated by the Poisson effect, and eventually affect the preferential precipitation orientation in Al-Cu alloy. Both mechanisms are expected to play important roles during stress/strain aging.

基于第一性原理计算方法探讨了铝合金应力/应变时效的可能机制,综合评估了时效温度和外加应力/应变对Al-Sc合金中Al3Sc固溶边界和Al-Cu合金中Al/θ''界面能的潜在影响。计算结果表明:在传统时效过程中引入外加拉应力/应变,声子态密度在高态区有红移现象,可以明显降低溶解熵;同时,导致相图中固溶线上移,表明外加拉应力/应变可降低Al3Sc在Al-Sc合金中的极限固溶度,从而增加析出相的最大可能体积分数。外加应力/应变对Al-Cu合金中不同取向的Al/θ''界面形成能有不同程度的影响,这种差别可以通过泊松效应进一步放大,从而影响到Al-Cu合金中析出相的择优取向。这2种机制在应力/应变时效中均可能发挥重要作用。