预压缩变形Mg-Zn-Y-Zr合金的微观组织及时效硬化效应
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摘要
对铸造Mg-8.14Zn-1.44Y-0.47Zr (%,质量分数)合金进行了0%～5%预压缩变形后,再经160℃进行等温时效处理。利用电子背散射衍射、高分辨率的透射电镜等分析手段研究了预变形镁合金的形变组织特征及其对后续时效组织、时效硬化效应的影响。结果表明:经预变形在镁合金基体中预置■拉伸孪晶和小角度晶界(位错),其小角度晶界所占百分比由1%预变形的2.6%增加到5%预变形的■拉伸孪晶变体数量随预变形量增加呈先增大后减少的趋势。160℃时效进程中,孪晶界成为准晶I-Mg_3Zn_6Y择优析出的有效衬底;而基体中存在的位错,提高了杆状或盘状β_1′-MgZn_2相析出密度,进而提高了镁合金时效初期析出速率及近峰值时效硬度; 5%预变形下达到近峰值时效硬度所需时间由未预变形的12 h缩短到6 h,近峰值时效硬度由未预变形的HV 81.5提高到HV 104.8。
The as-cast Mg-8.14 Zn-1.44 Y-0.47 Zr alloy was deformed by 0%～5% pre-compression and then isothermal aged at 160 ℃. The deformed microstructure and its influence on the subsequent aging microstructure and aging hardening effect were investigated by EBSD, TEM and et al. The results showed that the pre-deformed Mg alloy introduces ■ tensile twin and low-angle grain boundaries(dislocation), the percentage of low-angle grain boundary increases from 2.6% at the pre-deformation of 1% to 15.3% at the pre-deformation of 5%. With increasing the amount of pre-deformation, the number of ■ tensile twin firstly increases and then shows a decrease trend. During the 160 ℃ aging process, the twin boundary become an effective substrate for the preferential precipitation of quasicrystal I-Mg_3Zn_6Y. The presence of dislocations in the matrix promotes the precipitation of rod shaped or disc shaped β_1′-MgZn_2 phases, which improves the precipitation rate and the near-peak aging hardness at the initial period of aging. The time for reaching the near-peak age-hardening hardness at 5% pre-deformation is shortened from 12 h(without pre-deformation) to 6 h, and the near-peak hardness increases from HV 81.5(without pre-deformation) to HV 104.8.
The as-cast Mg-8.14 Zn-1.44 Y-0.47 Zr alloy was deformed by 0%～5% pre-compression and then isothermal aged at 160 ℃. The deformed microstructure and its influence on the subsequent aging microstructure and aging hardening effect were investigated by EBSD, TEM and et al. The results showed that the pre-deformed Mg alloy introduces ■ tensile twin and low-angle grain boundaries(dislocation), the percentage of low-angle grain boundary increases from 2.6% at the pre-deformation of 1% to 15.3% at the pre-deformation of 5%. With increasing the amount of pre-deformation, the number of ■ tensile twin firstly increases and then shows a decrease trend. During the 160 ℃ aging process, the twin boundary become an effective substrate for the preferential precipitation of quasicrystal I-Mg_3Zn_6Y. The presence of dislocations in the matrix promotes the precipitation of rod shaped or disc shaped β_1′-MgZn_2 phases, which improves the precipitation rate and the near-peak aging hardness at the initial period of aging. The time for reaching the near-peak age-hardening hardness at 5% pre-deformation is shortened from 12 h(without pre-deformation) to 6 h, and the near-peak hardness increases from HV 81.5(without pre-deformation) to HV 104.8.
引文
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[20]Ye J,Lin X P,Zhao T B,Liu N N,Xie H B,Niu Y,Teng F.Influence of pre-strain on the aging hardening effect of the Mg-9.02Zn-1.68Y alloy[J].Mater.Sci.Eng.A,2016,663:49.
[2]崔红卫.准晶增强Mg-Zn-Y合金的塑性加工及组织形成[D].济南:山东大学,2013.19.Cui H W.Plastical Deformation and Microstructural Formation of Icosahedral Quasicrystalline Reinforced Mg-Zn-YAlloys[D].Ji'nan:Shandong University,2013.19.
[3]陈振华.耐热镁合金[M].北京:化学工业出版社,2007.503.Cheng Z H.Heat-Resistant Magnesium Alloy[M].Beijing:Chemical Industry Press,2007.503.
[4]丁文江.镁合金科学与技术[M].北京:科学出版社,2007.365.Ding W J.Magnesium Alloy Science and Technology[M].Beijing:Chemical Industry Press,2007.365.
[5]刘庆.镁合金塑性变形机理研究进展[J].金属学报,2010,46(11):1458.Liu Q.Research progress of plastic deformation mechanism of magnesium alloys[J].Chinese Journal of Metals,2010,46(11):1458.
[6]Sasaki T T,Oh-Ishi K,Ohkubo T,Hono K.Enhanced age hardening response by the addition of Zn in Mg-Sn alloys[J].Scr.Mater.,2006,55(3):251.
[7]Mendis C L,Oh-Ishi K,Hono K.Enhanced age hardening in a Mg-2.4 at.%Zn alloy by trace additions of Ag and Ca[J].Scr.Mater.,2007,57(6):485.
[8]Gao X,Nie J F.Characterization of strengthening precipitate phases in a Mg-Zn alloy[J].Scr.Mater.,2007,56(8):645.
[9]Buha J.Reduced temperature(22~100℃)ageing of an Mg-Zn alloy[J].Mater.Sci.Eng.A,2008,492:11.
[10]Bettles C J,Gibson M A,Venkatesan K.Enhanced age-hardening behavior in Mg-4wt.%Zn micro-alloyed with Ca[J].Scr.Mater.,2004,51:193.
[11]Xu D K,Tang W N,Liu L,Xu Y B.Effect of W-phase on the mechanical properties of as-cast Mg-Zn-Y-Zr alloys[J].J Alloys Compd.,2008,461(1-2):248.
[12]Shia,Zhang W Z.A transmission electron microscopy investigation of crystallography ofτ-Mg32(Al,Zn)49precipitates in a Mg-Zn-Al alloy[J].Scr.Mater.,2011,64(2):201.
[13]Song B,Xin R,Sun L,Chen G,Liu Q.Enhancing the strength of rolled ZK60 alloys via the combined use of twinning deformation and aging treatment[J].Mater.Sci.Eng.,2013,582:68.
[14]Nie J F,Zhu Y M,Liu J Z,Fang X Y.Periodic segregation of solute atoms in fully coherent twin boundaries[J].Science,2013,340(6135):957.
[15]Rosalie J M,Somekawa H,Singh A,Mukai T.Effect of precipitation on strength and ductility in a Mg-Zn-Yalloy[J].J.Alloys Compd.,2013,550:114.
[16]■ J,Procházka I,Smola B,Stulíková I,■ ek V.Influence of deformation on precipitation process in Mg-15wt.%Gd alloy[J].J.Alloys Compd.,2007,430:92.
[17]辛明德,吉泽升.稀土元素在铸造镁合金中应用的研究现状及其发展趋势[J].中国稀土学报,2010,28(6):643.Xin M D,Ji Z S.Research situation and application prospects of rare earth in foundry magnesium alloy[J].Journal of the Chinese Society of Rare Earths,2010,28(6):643.
[18]耿振伟,肖代红.Mg-13Gd-2Nd-2Cu合金的显微组织与力学性能[J].中国稀土学报,2017,35(3):360.Geng Z W,Xiao D H.Microstructure and mechanical properties of Mg-13Gd-2Nd-2Cu alloy[J].Journal of the Chinese Society of Rare Earths,2017,35(3):360.
[19]贵云玮,李全安,周耀,陈晓亚.热处理对Mg-11Gd-2Y-5Sm-0.5Zr合金组织和力学性能的影响[J].中国稀土学报,2017,35(6):776.Gui Y W,Li Q A,Zhou Y,Chen X Y.Effect of heat treatment on microstructure and mechanical properties of Mg-11Gd-2Y-5Sm-0.5Zr alloy[J].Journal of the Chinese Society of Rare Earths,2017,35(6):776.
[20]Ye J,Lin X P,Zhao T B,Liu N N,Xie H B,Niu Y,Teng F.Influence of pre-strain on the aging hardening effect of the Mg-9.02Zn-1.68Y alloy[J].Mater.Sci.Eng.A,2016,663:49.