H. Kato, K. Sasaki, Hokkaido University, Sapporo, Japan
The martensitic transformation in manganese copper alloy is thermoelastic, and thus stress-induced transformation can occur. Superelasticity associated with the transformation, however, has never been observed, particularly as the stress-strain curve showing a stress plateau with a hysteresis loop. Small transformation strain, possible slip deformation, or work hardening due to the elastic constraint from surrounding grains in polycrystals, might be the reason. This study observed the curve in the single crystal of the austenite phase deformed at temperatures up to 30°C above the transformation temperature. The curve was symmetric between tension and compression; the superelastic strain was 0.2% and the stress hysteresis was as much as 8MPa. The hysteresis width was almost equal in magnitude to that of twin boundary motion in the martensite. The superelasticity might make certain contribution to the high damping capacity of the alloy.
Summary: This study observed superelasticity of manganese copper alloy single crystals. A typical stress-strain curve of superelasticity showing a stress plateau with hysteresis was obtained. The superelastic strain was about 0.2% and the stress hysteresis was as much as 8MPa. Possible contribution of superelasticity to the high damping capacity of the alloy is suggested.
