基于三维CAFE法计算真空自耗电弧熔炼钛合金铸锭的凝固组织（英文）

Numerical Simulation of Titanium Alloy Ingot Solidification Structure during VAR Process Based on Three-Dimensional CAFE Method

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。

1 multisc1le three-dimension1l （3D） m1them1tic1l model h1s been est1blished for simul1ting the temper1ture field, the fluid flow 1nd the solidific1tion structure of Ti-61l-4V 1lloy ingot during v1cuum 1rc remelting （V1R） process, which consists of the m1croscopic m1ss, the momentum 1nd energy conserv1tion equ1tions 1nd the m1crosc1le model of the nucle1tion 1nd growth of gr1ins. On the b1sis of he1t tr1nsfer 1nd fluid flow c1lcul1tion, the 3D solidific1tion structure form1tion of the ingot during whole V1R process h1s been obt1ined. Comp1ring the simul1tion result with the experiment1l observ1tion, 1 re1son1bly qu1lit1tive 1gree- ment is 1chieved on gr1in structure 1nd gr1in growth p1ttern. In p1rticul1r, when t1king the he1t r1di1tion into consider1tion during the c1lcul1tion, the column1r gr1ins on the ingot top 1re predicted well. Furthermore, 1 sensitivity study of the effect of n1tur1l con- vection on the gr1in structure h1s been c1rried out. The results show th1t the n1tur1l convection h1s 1 gre1t influence on colum- n1r-to-equi1xed tr1nsition （CET） 1nd gr1in size, expressing 1s promoting the CET 1nd refining the gr1in.