镍基单晶裂纹扩展路径研究  

Crack Propagation Paths and Fracture of Ni-Based Single Crystal

作　　者：温志勋[1] 苟文选[1] 岳珠峰[1] 

机构地区：[1]西北工业大学,陕西西安710072

出　　处：《稀有金属材料与工程》2007年第9期1549-1553,共5页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(10472094;50375124);国家航空基金(03B53003;02C53011);西北工业大学研究生创业种子基金(Z200620)资助项目

摘　　要：采用紧凑拉伸(CT)试样研究了3种不同温度(950,850,760℃)和3种不同晶体取向([001],[011],[111])下镍基单晶合金DD3的断裂特征,采用光学显微镜和扫描电子显微镜观察分析了裂纹扩展路径及断口形貌。采用率相关晶体滑移有限元程序对试件裂纹尖端三维分切应力场结构、裂纹启裂和扩展机制以及滑移系激活规律进行了模拟计算分析。结果表明:晶体取向和环境温度对裂纹启裂和扩展以及断裂强度和断裂形式有较大的影响,低温下裂纹扩展沿着特定的滑移带方向,与裂纹平面成一斜角,[001]裂纹取向下为45o,[011]裂纹取向下为53.7o,[111]裂纹取向下为90o,这使得宏观上裂纹扩展路径呈现Z字形外观。而温度较高时,发生的I型裂纹扩展与加载方向垂直。并且随着温度的升高,断裂形式逐步由脆性断裂转化为韧性断裂。The fracture behaviour of compact tension （CT） specimens of nickel-based single crystal superalloys DD3 has been studied at 760 ℃, 850 ℃ and 950 ℃ and three different crack crystallographic orientations of（001）[100], （011）[100] and （111）[0-11]. The macro crack growth paths, the fracture toughness and the micro fracture morphologies have been examined by optical microscope （OM） and scan electron microscope （SEM）. A crystallographic plastic finite element method （FEM） has also been used to analyze the resolved shear stress distribution ahead of the cracks. The experimental and FEM results show that the crystallographic orientations have much influence on the crack growth path, the fracture toughness of specimen, and the stress characterization ahead of the cracks. At low temperature, e.g. 760 ℃ or 850 ℃, the macroscopic crack growth path appears on the zigzag wave, but all the fracture surfaces are flat along the crack direction at high temperature, e.g., 950 ℃. FEM analysis shows that the deformation and fracture ahead of the crack take place in the specific slip planes for different crack orientations. For the three specimens tested at 760℃, the deflected angles of crack initiation direction with respect to crack plane are 45°, 53.7° and 90° in the order of crack orientations of （001）[100], （011）[100] and （ll 1）[0-11], respectively. The growth path of crack is agreement with the theoretical analyses by FEM, Furthermore, the temperature is another factor affecting the fracture of specimens. It is clear that the fracture mode of the CT specimens transfers from brittle to ductile with the temperature increasing.

关 键 词：镍基单晶体 CT试样 裂纹 断裂 

分 类 号：TG115.2[金属学及工艺—物理冶金]