ZM5石膏型反重力铸造热处理组织与性能研究

Microstructure and Mechanical Properties of Heat Treated ZM5 Magnesium Alloy by Gypsum Mold Counter Gravity Casting

通过对镁合金进行石膏型反重力铸造及时效热处理,研究了热处理工艺对ZM5镁合金显微组织及力学性能的影响,结果表明,经400~420℃固溶处理后,α相晶界上仍留有少量骨骼状β相。时效期间,β相优先在晶界非连续脱溶,进而在晶内连续脱溶,并进行竞争生长。随时效温度升高,由于固溶处理后晶体中空位浓度较高、铝在镁合金中体扩散系数增加较快,连续脱溶相体积分数增加。当时效温度为190℃时,镁合金试样性能较好,其抗拉强度为(257±5)MPa,延伸率(2.5±0.2)%,升高时效温度,β相粗化,力学性能下降。

Microstructures and mechanical properties of ZM5 alloy by gypsum mould counter gravity casting during heat treatment was investigated.The results showed that,after 400-420℃solution treatment,there was a small amount residual bone-likeβphase(Mg 17 Al 12)onαgrain boundary.During aging,continuous precipitatesβphase were preferentially initiated at some ofαgrain boundaries and then continuous precipitates appeared inαgrain interiors,both types of precipitates occur competitively.Due to high vacancy concentration and rapid increase of the volume diffusion coefficient for aluminium in magnesium,the volume fraction of continuous precipitates increased with ageing temperature.Optimal aging temperature with maximum mechanical properties is 190℃at which tensile strength is(257±5)MPa,elongation(2.5±0.2)%,the mechanical properties decrease withβphase coarsening.