近片层γ-TiAl基合金宏观塑性行为的尺度效应  

Effect of grain size on macroscopic plastic behavior of nearly lamellar γ-TiAl-based alloys

作　　者：苏继龙[1] 胡更开[2] 

机构地区：[1]福建农林大学机电工程学院 [2]北京理工大学应用力学系

出　　处：《中国有色金属学报》2006年第10期1684-1688,共5页The Chinese Journal of Nonferrous Metals

基　　金：国家自然科学基金资助项目(10325210)

摘　　要：将近片层-γTiAl基合金视为由等轴γ颗粒和多孪晶PST(polysynthetically twinned crystal)单晶颗粒组成的两相复合材料。基于非均质微极介质塑性理论,构建-γTiAl基合金整体有效微极柔度张量,将传统塑性割线模量法推广到微极材料,建立分析和预测-γTiAl基合金的塑性行为尺度效应的细观力学模型。结果表明:-γTiAl基合金的微结构尺度对其宏观塑性硬化行为存在显著的影响;近片层组织-γTiAl基合金中PST晶体颗粒的尺寸越小,合金中硬相夹杂PST颗粒的体积分数越大,合金材料相应的塑性硬化越明显;微极基体的塑性特征尺度与等轴γ晶粒的平均尺寸大小在同一数量级。An analytical micromechanical model in a framework of a micropolar continuum was proposed to investigate the size effect of macroscopic plastic behavior for a nearly lamellar γ-TiAl based alloy, which consisted of PST （polysynthetically twinned crystal） grains with random orientation. The WTiAI based alloy was considered as a twophase composite composed of micropolar matrix and PST particles. The Mori-Tanaka＇s method was advanced to e valuate the effective elastic moduli, and a new secant moduli method based on the second moment of strain and torsion of the matrix was extended to analyze the nonlinear behaviour of the γ-TiAl based alloy. The modeling results show that the size dependence is more pronounced when the PST particle＇s size approaches to the matrix characteristic length. The plastic stress of a nearly lamellar WTiAI based alloy increases with the decrease of PST grain size or with the increasing volume fraction of the PST grains. The characteristic length of plasticity of the micropolar matrix is approximately as the same order of magnitude as the average diameter of the matrix particles.

关 键 词：Γ-TIAL基合金 塑性 微极理论 尺度效应 细观力学 

分 类 号：TH142.2[一般工业技术—材料科学与工程]