定向凝固下Mg-1.5Gd合金的微观结构

Microstructure of Mg-1.5Gd alloy under directional solidification station

研究了不同速率下定向凝固Mg-1.5Gd合金的微观结构和微观偏析。研究发现,Mg-1.5Gd合金的凝固组织为典型胞晶结构,通过线性拟合得到胞晶间距与凝固速率的关系为:λ=130.2827V-0.2228,此结论与Trivedi模型拟合较好。通过Scheil模型计算热力学凝固路径,结合试验观察可确定凝固组织为α(Mg)相和α(Mg)+Mg5Gd二元共晶相。同时,通过Scheil模型计算所得Gd元素的微观偏析与EPMA测量结果基本一致。

The microstructure and micro segregation of Mg-1. 5Gd magnesium alloy under directional solidification station and different growth rates were studied. The microstructure was observed to be cellular structures and the relationship between cellular spacing（ λ） and growth rate V was established the relationship as λ = 130. 2827V^-0. 2228 by using a linear regression analysis,which was in good agreement with the calculated values by Trivedi model. Thermodynamics solidification path calculations by Scheil model and experimental observations confirm that the solidification microstructure in the alloy consists of primary α（ Mg） phase and binary eutectic α（ Mg） ＋ Mg5 Gd phase. Meanwhile,the micro segregation of the Gd element predicted by the Scheil model agrees reasonably with the electron probe microanalysis（ EPMA）measurements.