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Establishment of The Inspection Technique for Strength of Ti-Ni Shape Memory Alloys And Its Clarifying The Fracture Mechanisms

钛镍形状记忆合金强度检测技术的建立及其断裂机制的阐明

基本信息

批准号：
09650121
负责人：
YAJIMA Zenjiro
金额：
$ 2.05万
依托单位：
Kanazawa Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Establishment of the structural control method for the most suitable functional properties and the material inspection technique of Ti-Ni shape memory alloys are the main object of this project.Transformation temperatures, observation of microstructures and mechanical properties of variously heat-treated Ti-Ni-Co and Ti-Ni-Cu alloys were estimated. Mechanical properties of the alloys, which were at T < AィイD2fィエD2 (martensite phase), T = AィイD2fィエD2 (austenite + martensite phase) and T > AィイD2fィエD2 (austenite phase) ( T : test temperature, AィイD2fィエD2 : reverse transformation finish temperature ), were investigated by using a servo-hydraulic type material testing machine with an environmental chamber. Then fracture surfaces were observed by a high resolution scanning electron microscopy and X-ray diffractometer, and microstructure of near fracture region was observed by a transmission electron microscopy. The tensile deformation behaviors and fatigue properties are strongly affected by deformation speed. All the values of inflection stresses on the stress - strain curves increased with increasing tensile speed. The fatigue life obtained at 20 Hz was about 2 times longer than that at 0.5 Hz, referring to the maximum stress versus the number of cycles to failure curve. Striation patterns are clearly observed on the fatigue fracture surface, and the crack growth rates, dl/dN, were measured from these striation patterns. The deformation process model of Ti-Ni shape memory alloys was proposed on the basis of the above experimental results.

本课题的主要目标是建立Ti-Ni形状记忆合金最佳功能性能的组织控制方法和材料检测技术，估算了不同热处理的Ti-Ni-Co和Ti-Ni-Cu合金的相变温度、显微组织和力学性能。利用带环境室的伺服液压式材料试验机研究了T < A_（10）D_2f_（10）D_2（马氏体相）、T = A_（10）D_2f_（10）D_2（奥氏体+马氏体相）和T > A_（10）D_2f_（10）D_2（奥氏体相）（T：试验温度，A_（10）D_2f_（10）D_2：逆相变结束温度）下合金的力学性能。采用高分辨扫描电子显微镜和X射线衍射仪对断口进行了观察，并采用透射电子显微镜对断口附近的微观组织进行了观察。变形速度对合金的拉伸变形行为和疲劳性能有很大影响。应力-应变曲线上的拐点应力值均随拉伸速度的增加而增大.在20 Hz下获得的疲劳寿命比在0.5 Hz下获得的疲劳寿命长约2倍，参考最大应力与失效循环次数曲线。在疲劳断裂表面上清楚地观察到条纹图案，并且从这些条纹图案测量裂纹扩展速率dl/dN。在此基础上提出了Ti-Ni形状记忆合金的变形过程模型。