The Macroscopic Shape Change by Heating to High Temperature and Cooling in a Cu-Zn-Al Alloy

Sheets of a Cu-27.6Zn-3.8Al(mass%) alloy were quenched from a temperature in the β-phase range to 273 K and bent at 293 K. The sheets were then heated up to a temperature between 823 K and 1123 K and cooled down to room temperature.A distinct shape change, winding on cooling and unwinding on heating, was observed at high temperature during the thermal cycle, when the treating temperature did not exceed 1023 K. The higher the maximum temperature, the larger the amount of shape change. The total amount of winding on cooling was found to be larger than that of unwinding on heating, and these amounts were unchanged on repeating thermal cycles. Accordingly, the sheet was successively wound as the number of cycles increased.The shape change was found not to be affected by the external force, and so this phenomenon would be applied to production of RSM tools which work well even at high temperature.