纯钨闭塞式双通道等径角挤压数值模拟及实验研究
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摘要
采用数值模拟的方法分析单道次纯钨闭塞式双通道等径角挤压工艺的变形特点,并对比等径角挤压工艺和双通道等径角挤压工艺经过Bc路径4道次变形后的应变积累和分布特点。同时,为验证有限元模拟的准确性,开展了物理实验。结果表明,闭塞式双通道等径角挤压变形过程可分为初始阶段、镦粗成形阶段、剪切变形阶段和最终成形阶段。3种工艺经4道次变形后均发生较大的应变积累,但是由于闭式模膛对试样头部的镦粗作用,闭塞式双通道等径角挤压经过4道次变形后等效应变量最大,且等效应变分布最均匀。通过对模具应力的分析,闭塞式双通道等径角挤压和双通道等径角挤压工艺可以有效解决等径角挤压工艺冲头偏载问题,且试样经闭塞式双通道等径角挤压变形后具有较大的静水压力,提高了纯钨塑性,有利于进行多道次变形。闭塞式双通道等径角挤压工艺变形后的试样可分为4个区域:剪切变形区、伸长变形区、头部小变形区和尾部未变形区。
The deformation characteristics of the single-pass occlusive double equal channel angular pressing( O-DECAP) process for pure tungsten were analyzed by the numerical simulation method,and the strain accumulation and distribution characteristics of the equal channel angular pressing( ECAP) process and the double equal channel angular pressing( DECAP) process after four passes of the Bc path were compared. At the same time,in order to verify the accuracy of the finite element simulation,the physical experiment was carried out. The results show that the O-DECAP deformation process can be divided into initial stage,upsetting stage,shearing deformation stage and final forming stage. The strain accumulation occurs in all the three processes after 4 passes deformation,but the O-DECAP has the greatest equivalent strain with the most uniform distribution due to the upset deformation of the specimen head caused by the occlusive die. Through the analysis of stress distribution on die,O-DECAP and DECAP processes can effectively solve the eccentric loading problem during ECAP process. Moreover,the sample has a large hydrostatic pressure through the O-DECAP process,which improves pure tungsten plasticity and facilitates multi-pass deformation. The O-DECAP deformed sample is divided into four zones: shear deformation zone,elongation deformation zone,small deformation zone of the head and undeformed zone of the tail.
The deformation characteristics of the single-pass occlusive double equal channel angular pressing( O-DECAP) process for pure tungsten were analyzed by the numerical simulation method,and the strain accumulation and distribution characteristics of the equal channel angular pressing( ECAP) process and the double equal channel angular pressing( DECAP) process after four passes of the Bc path were compared. At the same time,in order to verify the accuracy of the finite element simulation,the physical experiment was carried out. The results show that the O-DECAP deformation process can be divided into initial stage,upsetting stage,shearing deformation stage and final forming stage. The strain accumulation occurs in all the three processes after 4 passes deformation,but the O-DECAP has the greatest equivalent strain with the most uniform distribution due to the upset deformation of the specimen head caused by the occlusive die. Through the analysis of stress distribution on die,O-DECAP and DECAP processes can effectively solve the eccentric loading problem during ECAP process. Moreover,the sample has a large hydrostatic pressure through the O-DECAP process,which improves pure tungsten plasticity and facilitates multi-pass deformation. The O-DECAP deformed sample is divided into four zones: shear deformation zone,elongation deformation zone,small deformation zone of the head and undeformed zone of the tail.
引文
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[3]王玉梅,张会.等径角挤压工艺的研究进展[J].材料导报,2014,28(9):87-91.WANG Yumei,ZHANG Hui.Research progress of equal channel angular pressing[J].Materials Review,2014,28(9):87-91.
[4]刘锋,王庆娟,杜忠泽,等.ECAP制备超细晶材料组织及其性能的研究进展[J].兵器材料科学与工程,2013,(4):103-106.LIU Feng,WANG Qingjuan,DU Zhongze,et al.Research progress in microstructure and property of ultrafine grain materials processed by ECAP[J].Ordnance Material Science and Engineering,2013,(4):103-106.
[5]AKBARIPANAH F,FERESHTEH-SANIEE F,MAHMUDI R,et al.The influences of extrusion and equal channel angular pressing(ECAP)processes on the fatigue behavior of AM60 magnesium alloy[J].Materials Science&Engineering A,2013,565(5):308-316.
[6]朱珍,王晓溪,董蔚霞,等.新型ECACE工艺下纯铝变形行为的有限元分析[J].热加工工艺,2016,45(13):175-178.ZHU Zhen,WANG Xiaoxi,DONG Weixia,et al.Finite element analysis on pure aluminum deformation behavior under new technology ECACE[J].Hot Working Technology,2016,45(13):175-178.
[7]LEE H H,YOON J I,KIM H S.Single-roll angular-rolling:Anew continuous severe plastic deformation process for metal sheets[J].Scripta Materialia,2018,146:204-207.
[8]李萍,张翔,薛克敏,等.纯铝等径角挤扭新工艺变形[J].塑性工程学报,2010,17(5):47-52.LI Ping,ZHANG Xiang,XUE Kemin,et al.Research on the new process of equal channel angular pressing and torsion of pure aluminum[J].Journal of Plasticity Engineering,2010,17(5):47-52.
[9]EIVANI A R.A new severe plastic deformation technique based on pure shear[J].Materials Science&Engineering A,2014,626:423-431.
[10]RAO V S,KASHYAP B,PRABHU N,et al.T-shaped equichannel angular pressing of Pb-Sn eutectic and its tensile properties[J].Material Science and Engineering A,2008,486(1):341-349.
[11]IWAHASHI Y,HORITA Z,NEMOTO N,et al.An investigation of microstruetural evolution during equal channel angular pressing[J].Acta Materialia,1997,45(11):4733-4741.
[12]WANG J,ZHAO G,CHEN L,et al.A comparative study of several constitutive models for powder metallurgy tungsten at elevated temperature[J].Materials&Design,2016,90:91-100.
[13]薛克敏,丁林高,李萍,等.TC4合金等径角挤压三维热力耦合有限元分析[J].哈尔滨工业大学学报,2009,41(12):228-231.XUE Kemin,DING Lingao,LI Ping,et al.Three-dimensional coupled thermo-mechanical FEM analysis of TC4 alloy during ECAP[J].Journal of Harbin Institute of Technology,2009,41(12):228-231.
[14]王晓溪,薛克敏,李萍.采用等径角挤扭工艺制备块体超细晶铝[J].中国有色金属学报,2014,24(6):1414-1421.WANG Xiaoxi,XUE Kemin,LI Ping.Fabrication of bulk ultrafine-grained pure aluminum using multi-pass equal channel angular pressing and torsion[J].The Chinese Journal of Nonferrous Metals,2014,24(6):1414-1421.