半固态等温热处理对AZ91D镁合金组织的影响

研究了 AZ91 D镁合金在半固态等温热处理过程中 ,等温时间、等温温度对其组织形态和初生相尺寸的影响 .研究发现 :在升温过程中 ,晶界处的共晶组织 (δ+γ)中的 γ相先发生溶解 ,之后 ,随着温度进一步升高 ,δ相又发生熔化分离 ,并在等温处理过程中逐渐变为球状 .当等温时间过长时 ,球状颗粒有长大的趋势 ,结果表明 :在 570℃时保温 60 min,可得到初生相尺寸在 50～ 80 μm的球状组织 .

Effects of semi-solid isothermal heat treatment on structure of magnesium alloy AZ91D

The effect of the time duration and the temperature magnitude on the microstructure and primary phase dimension during semi-solid isothermal heat-treatment (SSIT) is investigated.It is found experimentally that during the increasing of the temperature,the γ phase at grain interface of eutectic structures (δ＋γ) is dissolved first and then,with further increase of temperature δ phase melts and separates.The primary structure of AZ91D alloy takes gradually the form of spherical structure.When the isothermal time duration is excessive,the spherical structure will grow up.The results indicate that the dimension of the primary phase with spherical structure is 50—80 μm when SSIT is performed at 570 ℃ for 60 min.