Shuai Wang Koichi Tsuchiya Lei Wang Minoru Umemoto
材料科学技术（英文）
The deformed microstructures of a TiNi shape memory alloy were investigated in present study to clarify the deformation mechanism. It is found that the stress-strain curve was divided into three stages based on the deformation modes. The cause of martensitic stabilization effect was also interpreted by paying special attention to the deformed microstructures. Transmission electron microscopic examination revealed that at the early stage of deformation martensitic reorientation and compound twinning relieved some of the elastic strain energy stored in martensite, and this contributes to the martensitic stabilization effect. However, when deformation strain became larger, the density of dislocations increased correspondingly. Antiphase boundaries were also found. The degree of ordering was therefore decreased due to dislocations and antiphase boundaries.
So disordering was another cause of martensitic stabilization e®ect. In the middle stage of deformation martensitic stabilization was attributed to the two reasons above.
关键词:
TiNi shape memory alloy
,
transmission electron microscopy
,
ordering
,
dislocation
,
martensitic transformation.
Lijun HAN
,
Junjie ZHU
,
Lihong HAN
材料科学技术（英文）
The hysteresis unit system was introduced to mechanical structure behavior of the TiNi SMA joint based on the structure characteristics of the martensite variants in the joints, and some functions reflecting its inner structure characteristics and micro-behavior such as density function, phase transformation function were set up from micropoints. Finally, the structure behavior relationship and corresponding mathematic model reflecting the relationship among hysteresis strain, stress and phase transformation strain were provided, which could predict the stress-strain behavior of the TiNi SMA joint to large extent.
关键词:
TiNi shape memory alloy
,
null
,
null
杨成功
,
单际国
,
任家烈
材料科学与工艺
为探索焊缝金属逆相变温度随时效处理工艺的变化规律,利用OM、SEM、DSC对母材和经过时效处理的激光焊缝金属的组织形貌、析出相分布及逆相变温度进行了研究.结果表明,焊缝金属逆相变开始温度As和结束温度Af对焊接工艺参数不敏感,但时效处理能够明显提高焊缝金属的逆相变温度,其中As升高的更快,且焊缝金属As、Af与时效时间呈近线性关系.时效处理能明显提高焊缝金属的As、Af,其机理是时效促进了沉淀相析出,沉淀相对基体相的钉扎作用增加了低温马氏体的稳定性;另外,富Ni沉淀相的析出导致基体相Ni含量降低,也促进了As、Af升高.
关键词:
TiNi形状记忆合金
,
激光焊缝
,
马氏体逆相变温度
,
时效处理
李艳锋
,
米绪军
,
高宝东
,
尹向前
稀有金属材料与工程
研究了马氏体再取向(MR)和应力诱发马氏体转变(SIM)两种不同变形方式对Ni50.2Ti49.8合金拉伸性能及预应变后加热回复特性的影响.结果表明:拉伸变形中,MR变形方式的应力平台结束时的应变值较SIM变形方式大.在拉伸预应变处于应力平台阶段时,两种变形方式在相同预应变后加热回复有相同的记忆能力;在拉伸预应变大于应力平台时,两种变形方式在相同预应变后加热回复,SIM变形方式的逆相变温度和回复应变略高于MR变形方式.
关键词:
NiTi形状记忆合金
,
马氏体再取向
,
应力诱发马氏体转变
,
回复特性
