Mg-6Zn-1Cu-0.5Ce镁合金的非枝晶组织演变及机理
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摘要
半固态金属坯料部分重熔是半固态金属触变成形工艺的重要技术环节,采用等温热处理法对Mg-6Zn-1Cu-0.5Ce镁合金在部分重熔过程中的非枝晶组织演变过程和机理进行研究。结果表明:在半固态重熔初始阶段,Mg-6Zn-1Cu-0.5Ce合金沿晶界分布的共晶相逐渐向α-Mg基体中扩散溶解,达到共晶熔化温度后,剩余部分开始熔化。随着保温时间的进一步延长,为了降低系统的界面能,颗粒将发生合并长大。其中,非枝晶颗粒的分离是由液相沿亚晶界浸渗和根部重熔两种机制起主导作用。Mg-6Zn-1Cu-0.5Ce合金的最佳等温热处理工艺为保温温度600℃和保温时间25 min,采用该工艺处理后所得非枝晶颗粒平均尺寸为57μm,形状因子为1.16,固相率为68%。
Partial remelting is the important part of semi-solid metal(SSM) ingots forming technology.The non-dendritic microstructure evolution process and mechanism of Mg-6Zn-1Cu-0.5Ce magnesium alloy during partial remelting were investigated by isothermal heat-treatment.The results indicate that the eutectic phases of Mg-6Zn-1Cu-0.5Ce alloy initial microstructure distribute on grain boundary,which gradually dissolves into α-Mg matrix due to the diffusion of the solute,and the remainder is melted when the temperature up to eutectic melted during the initial stage of partial remelting.With the heat preservation time further extending,the semi-solid particles will combine and grow up to reduce the surface energy of the system.Furthermore,the appearance of subboundary and root remelting are the predominant separation mechanisms of particles during partial remelting.The best parameters of isothermal heat treatment are 600 ℃ in holding temperature and 25 min in holding time,obtaining the semi-solid microstructure with the average partial size of 57 μm,the roundness of 1.16 and the solid fraction of 68%.
Partial remelting is the important part of semi-solid metal(SSM) ingots forming technology.The non-dendritic microstructure evolution process and mechanism of Mg-6Zn-1Cu-0.5Ce magnesium alloy during partial remelting were investigated by isothermal heat-treatment.The results indicate that the eutectic phases of Mg-6Zn-1Cu-0.5Ce alloy initial microstructure distribute on grain boundary,which gradually dissolves into α-Mg matrix due to the diffusion of the solute,and the remainder is melted when the temperature up to eutectic melted during the initial stage of partial remelting.With the heat preservation time further extending,the semi-solid particles will combine and grow up to reduce the surface energy of the system.Furthermore,the appearance of subboundary and root remelting are the predominant separation mechanisms of particles during partial remelting.The best parameters of isothermal heat treatment are 600 ℃ in holding temperature and 25 min in holding time,obtaining the semi-solid microstructure with the average partial size of 57 μm,the roundness of 1.16 and the solid fraction of 68%.
引文
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[16]XU Hong,ZHANG Xin,WANG Chang-shun,HU Jin-chuan,WANG Cheng,LIU Chang-hua,ZHANG Wei-hua.Semi-solid moulding of AZ91D magnesium alloy[J].Materials Science Forum,2016,850(7):790-801.
[17]YAN Hong,RAO Yuan-sheng,CHEN Guo-xiang.Rheological behavior of semi-solid AZ91D magnesium alloy at steady state[J].Journal Wuhan University of Technology,2015,30(1):162-165.
[18]ZHANG Ying,MA Qiang,XU Jin-hua,XIE Shui-sheng,GENGMao-peng,GUO Hong-min,ZHAO Hai-bo.Numerical analysis on thermal field in rheocasting-rolling of semi-solid magnesium[J].Materials Science Forum,2011,675(6):957-960.
[19]MURAKAMI Y,OMURA N,LI M J,TAMURA T,MIWA K.Effect of injection speed on microstructure of AZ91Dmagnesium alloy in semi-solid injection process[J].Materials Transactions,2012,53(6):1094-1099.
[20]LI Dong-nan,CHEN Wen-zhe,TIAN Jun.Effect of heat treatment on microstructure and mechanical properties of semi-solid formed magnesium alloy AZ91D[J].2011,148(11):346-352.
[21]ZHAO Zu-de,CHEN Qiang,WANG Yan-bin,SHU Da-yu.Effect of predeformation on semi-solid microstructure of ZK60+RE magnesium alloy[J].Transactions of Nonferrous Metals Society of China,2009,19(3):535-539.
[22]ZHANG Guang-an,MA Cui-yan,ZHOU Qi.Semi-solid billets of AZ91D magnesium alloy prepared by forward extrusion/equal-channel angular pressing[J].Advanced Materials Research,2011,299(9):380-384.
[2]张红安,陈刚.铜/铝复合材料的固-液复合法制备及其界面结合机理[J].中国有色金属学报,2008,18(3):414-420.ZHANG Hong-an,CHEN Gang.Fabrication of Cu/Al compound materials by solid-liquid bonding method and interface bonding mechanism[J].The Chinese Journal of Nonferrous Metals,2008,18(3):414-420.
[3]CHEN Qiang,LIN Jun,SHU Da-yu,HU Chuan-kai,ZHAOZu-de,KANG Feng,HUANG Shu-hai,YUAN Bao-guo.Microstructure development,mechanical properties and formability of Mg-Zn-Y-Zr magnesium alloy[J].Materials Science and Engineering A,2012,554:129-141.
[4]FAN Z,LIU G,WANG Y.Microstructure and mechanical properties of rheo-diecast AZ91D magnesium alloy[J].Journal of Materials Science,2006,41(12):3631-3644.
[5]ZHANG Liang,WU Guo-hua,WANG Shao-hua,DINGWen-jiang.Effect of cooling condition on microstructure of semi-solid AZ91 slurry produced via ultrasonic vibration process[J].Transactions of Nonferrous Metals Society of China,2012,22(10):2357-2363.
[6]CHEN Qiang,YUAN Bao-guo,ZHAO Gao-zhan,SHU Da-yu,HU Chuan-kai,ZHAO Zu-de,ZHAO Zhi-xiang.Microstructural evolution during reheating and tensile mechanical properties of thixoforged AZ91D-RE magnesium alloy prepared by squeeze casting-solid extrusion[J].Materials Science and Engineering A,2012,537:25-38.
[7]张小立,李廷举,藤海涛,谢水生,金俊泽.等温热处理过程中铸态AZ91镁合金的微观组织演化[J].铸造,2007,56(10):1048-1052.ZHANG Xiao-li,LI Ting-ju,TENG Hai-tao,XIE Shui-sheng,JIN Jun-ze.Microstructure evolution of as-cast AZ91magnesium alloy during isothermal heat treatment[J].Foundry,2007,56(10):1048-1052.
[8]ZHAO Hu,HE Liang-ju,LI Pei-jie.Microstructure of asymmetric twin-roll cast AZ31 magnesium alloy[J].Transactions of Nonferrous Metals Society of China,2011,21(11):2372-2377.
[9]刘正,张奎,曾小勤.镁基轻质合金理论基础及其应用[M].北京:机械工业出版社,2002.LIU Zheng,ZHANG Kui,ZENG Xiao-qin.Academic basis and applications of the magnesium based light alloy[M].Beijing:China Machine Press,2002.
[10]黎文献.镁及镁合金[M].长沙:中南大学出版社,2005.LI Wen-xian.Magnesium and magnesium alloy[M].Changsha:Central South University Press,2005.
[11]CAO Li-jie,MA Guo-rui,TANG Chun-chong.Effects of isothermal process parameters on semid-solid microstructure of Mg-8%Al-1%Si alloy[J].The Chinese Journal of Nonferrous Metals,2012,22(10):2364-2369.
[12]ZHANG Y,WU G,LIU W,ZHANG L,PANG S,DING W.Microstructure and mechanical properties of rheo-squeeze casting AZ91-Ca magnesium alloy prepared by gas bubbling process[J].Materials&Design,2015,67:1-8.
[13]GUO H,ZHANG A,HU B,DING Y,LIU X.Refining microstructure of AZ91 magnesium alloy by introducing limited angular oscillation during initial stage of solidification[J].Materials Science and Engineering A,2012,532:211-219.
[14]ZHANG Liang,WU Guo-hua,WANG Shao-hua,DINGWen-jiang.Effect of cooling condition on microstructure of semi-solid AZ91 slurry produced via ultrasonic vibration process[J].Transactions of Nonferrous Metals Society of China,2012,22(10):2357-2363.
[15]乐启炽,崔建忠,路贵民,欧鹏.两相区铸造AZ91D半固态坯料的部分重熔工艺与组织演变[J].中国有色金属学报,2003,13(6):1488-1493.LE Qi-chi,CUI Jian-zhong,LU Gui-min,OU Peng.Microstructure evolution and partially remelting processing of two-phase-region casting AZ91D semisolid slurry ingot[J].The Chinese Journal of Nonferrous Metals,2003,13(6):1488-1493.
[16]XU Hong,ZHANG Xin,WANG Chang-shun,HU Jin-chuan,WANG Cheng,LIU Chang-hua,ZHANG Wei-hua.Semi-solid moulding of AZ91D magnesium alloy[J].Materials Science Forum,2016,850(7):790-801.
[17]YAN Hong,RAO Yuan-sheng,CHEN Guo-xiang.Rheological behavior of semi-solid AZ91D magnesium alloy at steady state[J].Journal Wuhan University of Technology,2015,30(1):162-165.
[18]ZHANG Ying,MA Qiang,XU Jin-hua,XIE Shui-sheng,GENGMao-peng,GUO Hong-min,ZHAO Hai-bo.Numerical analysis on thermal field in rheocasting-rolling of semi-solid magnesium[J].Materials Science Forum,2011,675(6):957-960.
[19]MURAKAMI Y,OMURA N,LI M J,TAMURA T,MIWA K.Effect of injection speed on microstructure of AZ91Dmagnesium alloy in semi-solid injection process[J].Materials Transactions,2012,53(6):1094-1099.
[20]LI Dong-nan,CHEN Wen-zhe,TIAN Jun.Effect of heat treatment on microstructure and mechanical properties of semi-solid formed magnesium alloy AZ91D[J].2011,148(11):346-352.
[21]ZHAO Zu-de,CHEN Qiang,WANG Yan-bin,SHU Da-yu.Effect of predeformation on semi-solid microstructure of ZK60+RE magnesium alloy[J].Transactions of Nonferrous Metals Society of China,2009,19(3):535-539.
[22]ZHANG Guang-an,MA Cui-yan,ZHOU Qi.Semi-solid billets of AZ91D magnesium alloy prepared by forward extrusion/equal-channel angular pressing[J].Advanced Materials Research,2011,299(9):380-384.