| Since the reverse shape memory effect(RSME) has been reported in a Cu-Zn-Al alloy, further studies have been done to ascertain the mechanism of this phenomenon and are reported to be caused by the bainitic transformation(β₂→α₁→α) on heating. But in the previous work, we suggested that the RSME in a Cu-Zn-Al alloy is not caused by the shear process involved in the bainitic transformation but by transformation from two-step transformed martensite(β₂→ β`₂→α`₂) t a phase by means of the XRD, TEM and micrographic observations. On heating after bending deformation in a parent phase state, the specimen shows both shape memory effect(303-473 K) and RSME(493-693 K) with increasing temperature, thus the shape change of sheet changed spontaneously. During aging at below and above of the bainitic transformation temperature, the sheet showed a small shape change but, heating to 693 K after aging, it showed a large shape change. Therefore the RSME occurs when the remaining two -step transformed α₂ phase introduced by bending deformation or heating is transformed into α phase and the bainitic transformation is not a principal mechanism although it contributes to the RSME. |
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