真空自耗电弧熔炼γ-TiAl合金铸锭凝固组织模拟

Prediction of Solidification Microstructure in γ-TiAl Alloy Ingots during Vacuum Arc Remelting

采用CAF模型对真空自耗电弧熔炼γ-TiAl合金铸锭凝固组织进行了数值模拟,在CAF模型中分别采用高斯分布连续形核模型和扩展KGT模型描述晶粒形核和枝晶尖端生长速率。研究了熔炼速率、界面传热系数和形核参数对铸锭凝固组织的影响。结果表明,增大熔炼速率或者增大最大形核密度,均有利于促进等轴晶形成,抑制柱状晶晶粒长大;增大平均形核过冷度或者增大界面传热系数,均有利于促进柱状晶的形成和晶粒长大;标准方差过冷度对铸锭凝固组织几乎没有影响。

A three dimensional cellular automaton-finite element model was developed to predict the solidification grain structures in γ-TiAl alloy ingots during vacuum arc remelting process,in which Gaussian distribution continuous nucleation model was adopted to describe the nucleation and the KGT model was extended to multi-component alloys to account for the growth kinetics of the dendrite tip.Effects of melting rate,heat transfer coefficient and nucleation parameters on the solidified microstructure evolution were investigated.The results reveal that with increasing in the melting rate or increasing in the maximum volume nucleation density,the formation of equiaxed grains is promoted,and the growth of columnar grains is restrained.Larger mean undercooling and larger heat transfer coefficient can increase grains size and number of columnar grain.The effects of variation of standard deviation on grain structure of the ingot can be ignored.