Effect of rare earth element Gd on microstructure and mechanical properties of Al-Si-Mg cast alloy
LIU Wen-yi, XU Cong, LIU Mao-wen, XIAO Wen-long, MA Chao-li
Key Laboratory of Aerospace Advanced Materials and Performance of Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191, China
Abstract：To systematically investigate the effect of rare earth element Gd on microstructure and mechanical properties of Al-Si-Mg(A357) cast alloy, A357 alloys with different Gd additions were investigated by OM, SEM, EPMA, XRD, DSC, TEM and tensile test. The results show that the addition of Gd can refine the grain and secondary dendrite arm spacing of the alloy. Besides, Gd refines eutectic Si, instead of transforming its morphology. The mechanical properties are improved by Gd addition due to obvious refinement of the grain and eutectic Si, the reduction of secondary dendrite arm spacing. For the A357-0.5Gd(mass fraction/%) alloy, the ultimate tensile strength(UTS) is 355MPa, which is 37MPa higher than that of the alloy without Gd. However, when increasing the Gd mass fraction to 1.0%, the formation of a high number of coarse Al2Si2 Gd results in the decrease of the mechanical properties of the alloy.The refinement mechanism of Gd was investigated.Combined with the TEM observation, it can be inferred that the Gd addition produces fewer twins but some nanosized particles within eutectic Si. The density of twins is not high enough to cause the morphology transition of eutectic Si. The refinement effect of Gd on eutectic Si may be attributed to the increase of constitutional overcooling and the formation of nanosized particles, inhibiting the growth of eutectic Si during solidification.
刘文祎, 徐聪, 刘茂文, 肖文龙, 马朝利. 稀土元素Gd对Al-Si-Mg铸造合金微观组织和力学性能的影响[J]. 材料工程, 2019, 47(6): 129-135.
LIU Wen-yi, XU Cong, LIU Mao-wen, XIAO Wen-long, MA Chao-li. Effect of rare earth element Gd on microstructure and mechanical properties of Al-Si-Mg cast alloy. Journal of Materials Engineering, 2019, 47(6): 129-135.
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2019, Vol. 47 
