Optimizing microstructure, shrinkage defects and mechanical performance of ZL205A alloys via coupling travelling magnetic fields with unidirectional solidification
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2021年第15期
论文作者：Lei Luo Liangshun Luo Yanqing Su Lin Su Liang Wang Jingjie Guo Hengzhi Fu
摘 要：ZL205A alloys tend to form disordered and defective microstructure due to the large solidification intervals and multi-phase. Accordingly, finding ways to effectively optimize the microstructure and mechanical performance is of great significance. In this regard, the coupling of travelling magnetic fields（TMF） with unidirectional solidification was used to continuously regulate the mushy zones of ZL205A alloys. Additionally, experiments are combined with simulations to systematically reveal the mechanisms on the optimizations at each stage of solidification process. Current findings demonstrate that different directional strong melt flows generated by TMF are responsible for these optimizations. Additionally, the effects of TMF on microstructure are different at each stage of solidification process. Specifically, downward TMF coupled with unidirectional solidification can refine and uniform the microstructure, decrease the formation of precipitation, promote the growth consistency of matrix phase α-Al growing along the<001> crystal orientation, reduce the secondary dendrites and overlaps between dendrites, eliminate the shrinkage defects, and increase the ultimate tensile strength, yield strength, elongation and hardness from 198.3 MPa, 102.2 MPa, 7.5 % and 82.3 kg mm-2 without TMF to 225.5 MPa, 116.1 MPa, 13.6 % and 105.2 kg mm-2. Contrastively, although upward TMF can reduce Al3Ti and refine α-Al, it increases the formation of Al6Mn, Al2Cu, secondary dendrites, overlaps between dendrites, and shrinkage defects; then it deflects and disorders the growth of α-Al, further to decrease the overall performance of alloys.
Lei Luo1，Liangshun Luo1，Yanqing Su1，Lin Su2，Liang Wang1，Jingjie Guo1，Hengzhi Fu1
1. National Key Laboratory for Precision Hot Processing of Metals, School of Materials Science & Engineering, Harbin Institute of Technology2. Office of International Cooperation, University of Science and Technology of China
摘 要：ZL205A alloys tend to form disordered and defective microstructure due to the large solidification intervals and multi-phase. Accordingly, finding ways to effectively optimize the microstructure and mechanical performance is of great significance. In this regard, the coupling of travelling magnetic fields（TMF） with unidirectional solidification was used to continuously regulate the mushy zones of ZL205A alloys. Additionally, experiments are combined with simulations to systematically reveal the mechanisms on the optimizations at each stage of solidification process. Current findings demonstrate that different directional strong melt flows generated by TMF are responsible for these optimizations. Additionally, the effects of TMF on microstructure are different at each stage of solidification process. Specifically, downward TMF coupled with unidirectional solidification can refine and uniform the microstructure, decrease the formation of precipitation, promote the growth consistency of matrix phase α-Al growing along the<001> crystal orientation, reduce the secondary dendrites and overlaps between dendrites, eliminate the shrinkage defects, and increase the ultimate tensile strength, yield strength, elongation and hardness from 198.3 MPa, 102.2 MPa, 7.5 % and 82.3 kg mm-2 without TMF to 225.5 MPa, 116.1 MPa, 13.6 % and 105.2 kg mm-2. Contrastively, although upward TMF can reduce Al3Ti and refine α-Al, it increases the formation of Al6Mn, Al2Cu, secondary dendrites, overlaps between dendrites, and shrinkage defects; then it deflects and disorders the growth of α-Al, further to decrease the overall performance of alloys.
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