Hysteretic and anhysteretic tensile stress-strain behavior of Ni-Fe(Co)-Ga single crystal: Experiment and theory

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• 作者：Anna Kosogor ; Victor A. L鈥檝ov ; Volodymyr A. Chernenko ; Elena Villa ; Jose M. Bar ; iaran ; Takashi Fukuda ; Tomoyuki Terai ; Tomoyuki Kakeshita
• 关键词：Hysteresis ; Stress&ndash ; strain loop ; Critical point ; Phase diagram
• 刊名：Acta Materialia
• 出版年：March, 2014
• 年：2014
• 卷：66
• 期：Complete
• 页码：79-85
• 全文大小：403 K

文摘

Recoverable strains have been measured in a single-crystalline Ni-Fe(Co)-Ga shape memory alloy in the course of tensile tests performed at different temperatures. Two substantially different types of deformation process were observed above the martensitic transformation temperature, T_M 鈮?#xA0;200 K. An unusual anhysteretic stress-strain behavior characterized by an enormous (鈭?4%) nonlinear deformation was found above 320 K, while stress-strain loops showing a pronounced hysteresis were obtained below this temperature. A sudden reduction of hysteresis was explained using the theoretical stress-temperature diagram of ferroelastic phase transitions. It has been shown that this almost anhysteretic deformation can occur when the temperature of the deformed alloy exceeds the critical value corresponding to the endpoint of the phase transition line in the phase diagram. A theoretical analysis showed that above the critical temperature a very small residual hysteresis (鈭? MPa) may be caused by the reconfiguration of crystal defects during the deformation cycle.