Zhonggang SUN
金属学报(英文版)
The TEM and HRTEM were utilized to investigate the phase transformation of hydrogenated Ti-6Al-4V alloys (0 wtpct-0.9 wt pct H) treated by annealing and quenching from β field. The results indicate that the orthorhombic α'' martensite and β phase appear progressively with the increase of hydrogen concentration. On the other hand, hydrides with sizes of 2-5 nm are observed in the specimens containing more than 0.6 wt pct hydrogen. The formation of α'' and twins can be attributed to the internal stress caused by solid solution of hydrogen and hydrides precipitation.
关键词:
Ti-6Al-4V alloys
,
Martensitic transformation
,
Hydrogenation
,
Hydride
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.
