固溶处理冷却介质温度对Mg-13Gd-4Y-2Zn-0.5Zr合金时效组织及硬度的影响

Effect of cooling media temperature for solid solution treatment on as-aged microstructure and hardness of Mg-13Gd-4Y-2Zn-0. 5Zr alloy

以高稀土含量Mg-13Gd-4Y-2Zn-0.5Zr镁合金为研究对象利用SEM、EBSD和硬度等测试方法,研究不同固溶处理参数下,固溶处理冷却介质温度对合金时效组织和硬度的影响规律。试验结果表明,合金在520℃×24h固溶处理条件下,其冷却介质温度对硬度及组织的影响最为显著,随着固溶冷却介质温度降低,硬度值逐渐增大。同时,固溶冷却介质温度越低,点状Mg5(Gd,Y)相和片层相在时效中析出的数量越多。当固溶冷却介质温度较高时,时效过程中则以针状Mg5(Gd,Y)相析出为主且层错相析出较少。此外,由于在低温或短时固溶处理下,合金的晶粒尺寸变化较小,在后续时效过程中细晶强化作用高于析出强化,所以合金的固溶冷却介质温度对时效组织及硬度影响较弱。

Effect of cooling media temperature for solid solution treatment under different parameters on as-aged microstructure and hardness of high rare earth Mg-13 Gd-4 Y-2 Zn-0.5 Zr magnesium alloy was studied by SEM,EBSD and Vickers hardness testing.The results show that when solution treated at 520℃× 24 h,the cooling medium temperature has the most significant effect on the hardness and microstructure,and the hardness value increases gradually with the decrease of cooling media temperature.Moreover,the lower the cooling medium temperature,the more the dot-like Mg5(Gd,Y) phase and lamellar phase are precipitated during aging.However,when the cooling media temperature is high,needle-shaped Mg5(Gd,Y) phase is mainly precipitated,while the phases with stacking faults(SFs) are less.In addition,because the grain size of the alloy is not changed obviously under low temperature or short time solid solution treatment,the effect of refinement strengthening is higher than that of the precipitation strengthening in subsequent aging process,thus the cooling media temperature for solid solution treatment has a weak effect on the hardness and microstructure.