Effect of Hydrogen Doping on Stress-Induced Martensitic Transformation in a Ti-Ni Shape Memory Alloy
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i-Ni shape memory alloys (SMAs) are widely used in commercial products due to their unique superelastic property.[1–4] This property depends on the stress-induced austenite-to-martensite phase transformation in Ti-Ni SMAs.[1–6] It has been pointed out by many researchers that the phase transformation and mechanical behaviors of Ti-Ni SMAs could be significantly affected by hydrogen absorption.[7–13] Since hydrogen atoms can inadvertently enter Ti-Ni SMAs through electrolysis, pickling, or other means in a
ZHENXING LI, XIAO LIANG, HONG CHEN, and ZHU LI are with the State Key Lab of Metal Matrix Composite, School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240, P.R. China. FEI XIAO is with the State Key Lab of Metal Matrix Composite, School of Materials Science and Engineering, Shanghai Jiao Tong University and also with the Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan. Contact e-mail: [email protected] XUEJUN JIN is with the Institute of Advanced Steels and Materials, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P.R. China. TAKASHI FUKUDA is with the Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University Manuscript submitted November 20, 2018. Article published online May 14, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
hydrogen-containing environment, the interaction of hydrogen with Ti-Ni SMAs is a key concern in the performance of the material. Several studies have revealed the effect of hydrogen on the thermal-induced martensitic transformation (MT) of Ti-Ni SMAs.[14–16] It is commonly agreed that the thermal-induced MT of Ti-Ni SMAs is suppressed by hydrogen charging. The transformation temperature decreases and the latent heat reduces.[14,15] The reason for the suppression was explained by the trapped hydrogen, which acts as a barrier so as to block the progress of MT. This blocking effect of hydrogen possibly affects the progress of stress-induced MT as well. In fact, it is found in a hydrogen-charged Ti-Ni alloy that the critical stress for inducing MT increases and fracture occurs during the stress-induced MT. Considering these results, Runciman et al. affirmed that hydrogen stabilizes the austenite phase and suppresses the MT.[14] However, a recent research showed that hydrogen ensures the stability of the phase in which the charging process occurs, rather than the austenite phase.[17] Therefore, the mechanism of the effect of hydrogen on the stress-induced MT is still unclear. Moreover, no report has been made on the in situ structural evolution during the stress-induced MT of hydrogen-charged Ti-Ni SMAs. In this study, we examined the influence of hydrogen on stress-induced MT in a Ti-50.8Ni (at. pct) alloy by in situ X-ray analysis. In addition, we observed the diffusion of hydrogen into the interior of specimen during the aging process by SEM-TOF-SIMS. A hot-rolled
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