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建立三维多尺度数学模型计算Ti-6Al-4V合金铸锭真空自耗电弧熔炼(VAR)过程中的温度场、流场及凝固组织的形成。该模型包括宏观质量、动量及能量守恒方程和介观晶粒形核生长模型。在传热与流动计算的基础上,模拟铸锭VAR过程中的三维凝固组织的形成。对比计算结果与实验观察可知,两者在晶粒结构与晶粒生长方式方面吻合较好。当考虑VAR过程中熔池表面的辐射换热后,铸锭顶部的柱状晶被很好地呈现。最后,考察了自然对流对铸锭凝固组织的影响,计算结果表明自然对流对柱状晶-等轴晶转变(CET)及晶粒尺寸影响较大,表现为促进CET及细化晶粒。
A three-dimensional multi-scale mathematical model was established to calculate the temperature field, flow field and the formation of solidified structure in vacuum consumable arc melting (VAR) process of Ti-6Al-4V alloy ingot. The model includes macroscopic mass, momentum and energy conservation equations and mesoscopic grain growth model. Based on the heat transfer and flow calculation, the formation of three-dimensional solidified structure in ingot VAR was simulated. Comparing the calculation results with the experimental observations, we can see that the two are in good agreement with the grain structure and grain growth mode. When considering the radiation heat transfer on the surface of molten pool during VAR, the columnar crystals on the top of ingot are well presented. Finally, the influence of natural convection on ingot solidification was investigated. The calculated results show that natural convection has a great influence on CET and grain size, which is promoted by CET and grain refinement.