Simulation of Macrosegregation and Shrinkage Cavity in an Al-4.5 Wt Pct Cu Ingot Using a Four-Phase Model
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MACROSEGREGATION is an inevitable defect in terms of macroscopic heterogeneity of solutal distribution during casting solidification. The formation mechanism of this defect has been studied since the early period of the last century. The general conclusion shows that the relative motion between the solid and surrounding melt plays an important role in determining the final macrosegregation.[1] Basically, the relative motion is attributed to the density differences between the grains and the bulk melt, thermosolutal convection, and solid sedimentation. Actually, the solidification conditions, FENGLI REN, DUANXING CAI, QIAODAN HU, and MINGXU XIA are with the School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. HONGHAO GE is with the Institute of Laser Advanced Manufacturing, Zhejiang University of Technology, Hangzhou 310014, China. JUN LI is with the School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, China and also with the Department of Engineering, University of Leicester, Leicester, LE1 7RH, UK. JIANGUO LI is with the School of Materials Science and Engineering, Shanghai Jiao Tong University and also with the Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, China. Contact email: [email protected] Manuscript submitted January 15, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
e.g., initial melt temperature, mold temperature, and initial flow pattern, also have effects on the relative motion and lead to different patterns of macrosegregation. A large number of experiments have been done to investigate the macrosegregation in ingots.[2] However, it is difficult to observe the formation procedure of macrosegregation in situ during the solidification. In addition, there is extra time and cost consuming for the postsolidification experimental investigation on large scale steel ingot. Hence, with the development of computational capability, simulation has been an effective way to investigate the formation of macrosegregation. People have tried different models to understand the formation of macrosegregation since the first mushy zone model presented by Fujii et al.[3] to study channel-type segregation. After that, Wang and Beckermann[4,5] introduced an equiaxed dendritic model that considered the melt convection and the grain sedimentation but neglected the influence of columnar phase. In the 2000s, Wu and Ludwig[6] extended the previous works and presented a mixed three-phase model considering the interaction between liquid, globular equiaxed, and columnar phases during solidification. Their model successfully predicted the interaction or competition growing between the columnar and equiaxed phases and the occurrence of columnar-to-equiaxed transition (CET) in a laboratorial scale
steel ingot. A further effort[7,8] was made to extend this mixed three-phase model with the consideration of interdendritic melts in both columnar and equiaxed phases using the volume averaged m
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