汽车发动机用ZL205合金的变质处理及性能研究

Study on Modification and Properties of ZL205 Alloy for Automobile Engine

研究了未变质和稀土Pr变质ZL205合金在不同温度和外加应力条件下的显微形貌演变规律,分析了Pr变质ZL205合金高温蠕变作用机制。结果表明,在相同蠕变温度和外加应力作用下,Pr变质的稳态蠕变速率均低于未变质ZL205合金,且0.3%Pr变质的稳态蠕变速率较未变质ZL205合金低3~4倍;经Pr变质处理的表观应力指数高于相同蠕变温度的未变质ZL205合金,且0.3%Pr变质的表观应力指数最高,未变质和Pr变质的蠕变控制机制为高温位错滑移或者攀移;添加Pr变质后,合金中纳米θ′相的析出增多,纳米θ′相的高温稳定性得到提高;蠕变前后,0.3%Pr变质合金晶界处颗粒状Al11Pr3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 evolution of the microstructure of unmodified and Pr metamorphic ZL205 alloy at different temperatures and applied stresses was investigated,and the mechanism of high temperature creep of Pr metamorphic alloy was investigated.The results show that the steady creep rate of Pr metamorphic alloy is lower than that of the unmetamorphic alloy,and the steady creep rate of 0.3%Pr modified alloy is lower than that of the unmodified alloy by 3-4 times under the same creep temperature and applied stress;the apparent stress exponent of Pr metamorphic alloy are higher than that of unmodified alloy under the same temperature creep,the apparent stress exponent of 0.3% Pr metamorphic alloy is the highest,and the creep control mechanism of ZL205 alloy with and without Pr modification is high temperature dislocation slip or climb;after the modification of ZL205 alloy by adding Pr element,the amount of nano-phase θ′ in the alloy increases,and the high temperature stability of the nano-phase θ′ is improved;the morphology of granular Al11 Pr3 phase in the grain boundaries of 0.3%Pr metamorphic alloy is not significantly changed before and after creep,which could play a role in preventing the grain boundary movement during the high temperature creep.