微观组织演变对细晶Mg-Y-Nd合金超塑性性能的影响
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摘要
在初始应变速率为2×10~(-2)～4×10~(-4)s~(-1),温度为683～758 K的条件下,对用水下搅拌摩擦加工制备的细晶Mg-Y-Nd合金进行高温拉伸实验,研究了微观组织演变对其超塑性性能的影响。结果表明:因为具有细小均匀的微观组织和良好的热稳定性,Mg-Y-Nd合金在733 K和3×10~(-3)s(-1)初始应变速率下表现出最大的伸长率(967%),在758 K和2×10~(-2)s(-1)条件下表现出最优的高应变速率超塑性(900%)。在高温下暴露时间过长导致α-Mg晶粒和第二相颗粒显著长大,使试样的伸长率明显降低;因为第二相颗粒与镁基体之间有良好的变形协调性,在相界处不会产生明显的应力集中,裂纹主要在晶界生成。
Superplastic performance of the submerged friction stir processed Mg-Y-Nd alloy was assessed by initial strain rates in range of 2×10-2 to 4×10-4 s-1 at temperatures in range of 683 to 758 K, aiming to reveal the correlation of the microstructure evolution and the superplastic performance of the alloy.Results show that due to the fine-grained and stable microstructure, the alloy exhibits the maximum elongation of 967% by strain rate of 3×10-3 s-1 at 733 K, and the excellent high strain rate superplasticity of900% by 2×10-2 s-1 at 758 K respectively. The average size of α-Mg grains and secondary phase particles remarkably increased when the alloy subjected to high temperature tensile tests for long time, as a result,the elongation of the alloy significantly decreased. Cavities easily formed at grain boundaries instead of the interface of secondary particles and matrix, which may be responsible to the good deformation compatibility between particles and matrix.
Superplastic performance of the submerged friction stir processed Mg-Y-Nd alloy was assessed by initial strain rates in range of 2×10-2 to 4×10-4 s-1 at temperatures in range of 683 to 758 K, aiming to reveal the correlation of the microstructure evolution and the superplastic performance of the alloy.Results show that due to the fine-grained and stable microstructure, the alloy exhibits the maximum elongation of 967% by strain rate of 3×10-3 s-1 at 733 K, and the excellent high strain rate superplasticity of900% by 2×10-2 s-1 at 758 K respectively. The average size of α-Mg grains and secondary phase particles remarkably increased when the alloy subjected to high temperature tensile tests for long time, as a result,the elongation of the alloy significantly decreased. Cavities easily formed at grain boundaries instead of the interface of secondary particles and matrix, which may be responsible to the good deformation compatibility between particles and matrix.
引文
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[2]Langdon T G.Twenty-five years of ultrafine-grained materials:Achieving exceptional properties through grain refinement[J].Acta Mater.,2013,61:7035
[3]Chen Z H,Liu J W,Chen D,et al.Deformation mechanisms,current status and development direction of superplastic magnesium alloys[J].Chin.J.Nonferrous Met.,2008,18:193(陈振华,刘俊伟,陈鼎等.镁合金超塑性的变形机理、研究现状及发展趋势[J].中国有色金属学报,2008,18:193)
[4]Kandalam S,Sabat R K,Bibhanshu N,et al.Superplasticity in high temperature magnesium alloy WE43[J].Mater.Sci.Eng.,2017,687A:85
[5]Chen F F,Huang H J,Xue P,et al.Research progress on microstructure and mechanical properties of friction stir processed ultrafine-grained materials[J].Chin.J.Mater.Res.,2018,32(1):1(陈菲菲,黄宏军,薛鹏等.搅拌摩擦加工超细晶材料的组织和力学性能研究进展[J].材料研究学报,2018,32(1):1)
[6]Hofmann D C,Vecchio K S.Submerged friction stir processing(SFSP):An improved method for creating ultra-fine-grained bulk materials[J].Mater.Sci.Eng.,2005,402A:234
[7]Cao G H,Zhang D T,Luo X C,et al.Effect of aging treatment on mechanical properties and fracture behavior of friction stir processed Mg-Y-Nd alloy[J].J.Mater.Sci.,2016,51:7571
[8]Chai F,Zhang D T,Zhang W W,et al.Microstructure evolution during high strain rate tensile deformation of a fine-grained AZ91magnesium alloy[J].Mater.Sci.Eng.,2014,590A:80
[9]Wang X,Chen D,Xiao D,et al.Superplasticity of Mg-Al-Ca alloys with high Ca/Al ratio[J].Mater.Rev.,2016,30(10):71(王新,陈鼎,肖迪等.高Ca/Al比的Mg-Al-Ca合金的超塑性[J].材料导报,2016,30(10):71)
[10]Kim W J,Lee K E,Park J P,et al.Microstructure and superplasticity of Mg-Al-Ca electromagnetic casting alloys after hot extrusion[J].Mater.Sci.Eng.,2008,494A:391
[11]Frost H J,Ashby M F.Deformation-Mechanism Maps[M].Oxford,UK:Pergamon Press,1982
[12]Kim W J,Moon I K,Han S H.Ultrafine-grained Mg-Zn-Zr alloy with high strength and high-strain-rate superplasticity[J].Mater.Sci.Eng.,2012,538A:374
[13]Watanabe H,Mukai T,Ishikawa K,et al.Realization of high strain rate superplasticity at low temperatures in a Mg-Zn-Zr alloy[J].Mater.Sci.Eng.,2001,307A:119
[14]Barnes A J.Superplastic forming 40 years and still growing[J].J.Mater.Eng.Perform.,2007,16:440
[15]Figueiredo R B,Langdon T G.Strategies for achieving high strain rate superplasticity in magnesium alloys processed by equal-channel angular pressing[J].Scr.Mater.,2009,61:84
[16]Luo Z A,Xie G M,Ma Z Y,et al.Effect of yttrium addition on microstructural characteristics and superplastic behavior of friction stir processed ZK60 alloy[J].J.Mater.Sci.Technol.,2013,29:1116
[17]Tang W N,Chen R S,Han E H.Superplastic behaviors of a MgZn-Y-Zr alloy processed by extrusion and equal channel angular extrusion[J].J.Alloys Compd.,2009,477:636
[18]Yang Q,Xiao B L,Zhang Q,et al.Exceptional high-strain-rate superplasticity in Mg-Gd-Y-Zn-Zr alloy with long-period stacking ordered phase[J].Scr.Mater.,2013,69:801
[19]Li L,Zhang X M,Deng Y L,et al.Effect of second phase on superplastic deformation of extruded rod of Mg-Gd-Y-Zr alloy[J].Chin.J.Nonferrous Met.,2010,20:10(李理,张新明,邓运来等.第二相在Mg-Gd-Y-Zr合金挤压棒超塑性变形中的作用[J].中国有色金属学报,2010,20:10)