杨钢黄崇湘吴世丁张哲峰
金属学报
研究了304L奥氏体不锈钢在严重塑性变形(等通道转角挤压, ECAP)下发生形变诱导马氏体转变的微观特征, 包括形核特征、长大方式和相变晶体学, 探讨了粗大晶粒和亚微米晶粒发生马氏体相变的异同和微观机理. 结果表明: 粗大奥氏体晶粒发生相变时, 马氏体主要形核于微观剪切带(包括层错、变形孪晶和ε相等)的相互交割处, 马氏体与奥氏体之间为K---S(Kurduumov---Sachs)关系, 而不是西山(Nishiyama---Wassermann)关系; 亚微米奥氏体晶粒发生相变时, 马氏体则多在奥氏体晶界处形核, 马氏体与奥氏体之间仍为K---S关系.
关键词:
奥氏体不锈钢
,
equal channel angular pressing
,
submicron grain
,
martensitic transformation
,
microscopic mechanism
Ping YANG
金属学报(英文版)
Experiments show that special processing techniques such as asymmetrical rolling (ASR), equal channel angular pressing (ECAP) and equal channel angular rolling (ECAR) can weaken the basal texture of the magnesium alloys and therefore improve their plasticity. However, the deformation mechanisms related are different. In this paper, we determine the deformation mechanisms activated during ASR, ECAP and ECAR by calculation of orientation factors. Analysis shows that during ASR the shear stress σ13 on the rolling plane of the samples obviously weakens the basal slip and tension twinning that all produce basal texture and improve plasticity due to the promotion of tilt basal texture. During ECAP the shear stress σs on the intersecting plane of two channels promotes tension twinning in the basal
oriented grains, whereas under ECAR the shear stress σ13 induced by roller friction on the rolling plane produces the shear stress σs on the intersection plane of the two channels that also promotes tension twinning. Although the shear strain is lower in ECAR than in ECAP, the channel clearance in ECAR facilitates tension twinning.
关键词:
Magnesium
,
asymmetrical rolling
,
equal channel angular pressing
,
equal channel angular rolling
,
deformation
王晓梅
,
陈银佳
,
韩其琛
,
陈爱英
,
李翔
,
刘芳
,
潘登
稀有金属材料与工程
为了优化室温下等通道转角挤压纯钛工件的几何形状,采用三维有限元软件模拟了纯钛工件的变形行为.通过对比分析工件形状和尺寸对损伤因子、挤压力以及剪切带处应变速率分布等参数的影响,获得了工件最佳几何形状.仿真结果表明,方条形工件的损伤因子大于圆棒型工件,且高于纯钛材料的临界损伤因子,表明方条形工件不利于变形,易产生表面裂纹.3D模拟结果表明,直径为15mm的圆棒型工件具有最小的损伤因子,适中的挤压载荷以及相对均匀的应变分布.依据仿真结果提供的最佳工件,即直径为15mm的圆棒型工件,室温下成功挤压出直径15mm的纯钛圆棒.挤压后样品截面上硬度分布均匀,与3D仿真所预示的均匀应变分布相一致.
关键词:
有限元法
,
钛
,
等通道转角挤压
,
变形
