等温热处理对AZ91D+Ce镁合金半固态组织的影响

研究了等温热处理对AZ91D+Ce镁合金半固态组织的影响,获得了较理想的球状或类球状晶粒组织。结果表明,在等温热处理的过程中,加入稀土Ce会阻碍原子向固相粒子聚集和结合,抑制固相颗粒的长大,形成细小圆整的半固态组织。随等温热处理温度的升高,原子活动能力增强,熔化速度加快,液相量增加,固相颗粒尺寸先减小后增大。在等温初始阶段,熔化对初生固相颗粒尺寸起决定作用,使得颗粒尺寸减小。但是,随等温时间的进一步增加,由于合并粗化和Ostwald熟化的作用,固相颗粒开始长大。

Effect of isothermal heat treatment on the microstructure of semi-solid AZ91D Ce magnesium alloy

The effect of isothermal heat treatment on the microstructure of semi-solid AZ91D Ce magnesium alloy was investigated and the ideal globular and near-globular microstructure was obtained. The results show that the rare earth Ce can hider aggregating and associating of the primary solid particles, inhibit growing of the solid particles and form fine well-distributed round semi-solid microstructure. During higher isothermal heat treatment temperature, there is more liquid phase due to the stronger movability of atoms and faster melting rate of solid particles. The size of solid particles is decreased first and then increased. The size of solid particles is mainly decided by melting in initial stage of isothermal heat treatment. Therefore, the size of solid particles is decreased. With further increasing of the isothermal heat treatment time, the size of solid particles is mainly decided by coarsening mechanism and Ostwald ripening and then the size of solid particles is increased.