铸造ZL205A合金的变质处理与蠕变性能研究

Modification and Creep Properties of Cast ZL205A Alloy

对比分析了未变质和不同La含量变质的ZL205A合金在180、200和220℃的高温蠕变性能,探索了未变质和La变质ZL205A合金在不同温度和外加应力条件下的显微形貌演变,分析了La变质ZL205A合金的高温蠕变作用机制。结果表明,在相同蠕变温度和外加应力作用下,La变质ZL205A合金的稳态蠕变速率都要低于未变质ZL205A合金,且在La含量为0.3%时最低;经过La变质处理的ZL205A合金的表观应力指数都高于相同蠕变温度下的未变质ZL205A合金,且0.3%的La变质ZL205A合金的表观应力指数最高,未变质和La变质ZL205A合金的蠕变控制机制为高温位错滑移或者攀移;La变质处理后,ZL205A合金中纳米θ′相的析出数量有所增多,且纳米θ′相的高温稳定性得到改善;蠕变前后,0.3%的La变质ZL205A合金晶界处断续颗粒状Al11La3相的形貌未发生明显变化,在高温蠕变过程中可以起到阻碍晶界运动的作用。

The creep properties of unmodified and modified Al-Cu alloy with different content of La at 180℃,200 ℃ and 220 ℃ were analyzed comparatively.The microstructure evolution of unmodified and La modified ZL205 Aalloy at different temperature and applied stress was observed,and the mechanism of high temperature creep of La modified ZL205 Aalloy was described.The results reveal that,under the same creep temperature and applied stress,the steady creep rate of La modified ZL205 Aalloy is the lower than that of the unmodified ZL205 Aalloy,and the steady creep rate of 0.3%La modified ZL205 Aalloy is the lower 3~4times than that of the unmodified ZL205 Aalloy.The apparent stress exponent of La modified ZL205 Aalloy is the higher than that of unmodified ZL205 Aalloy under the same temperature,and the apparent stress exponent of 0.3%La modified ZL205 Aalloy exhibits the highest value.The creep control mechanism of ZL205 Aalloy with and without La modification is characterized by high temperature dislocation slip or climb.After the modification of ZL205 Aalloy by adding La element,the amount of nano phase in the alloy is increased,and the high temperature stability of the nano phase is improved.The morphology change of discontinuous granular Al11La3 phase at the grain boundaries of0.3% La modified ZL205 Aalloy can be ignored before and after creep,which can play a role in preventing the grain boundary movement during the high temperature creep.