The influence of short-range disorder on the martensitic transformation in Cu-Zn and Cu-Zn-Al alloys.

Abstract

The transformation temperature, Aís in C u-Zn and C u-Zn-A l alloys is changed by quenching from temperatures, TQ > M s. In Cu-Zn the quench from TQ leads to an increase in 1Vf„ whereas in Cu-Zn-Al, Aís is lowered compared to samples that are slowly cooled or have been aged at room temperature after the quench. The effect is ascribed to quenched-in disordered atom pairs in the long range ordered matrix. The formation energies for disordered pairs have been calculated, and it is shown that in C u-Zn nearest-neighbour pairs increase M„ whereas in C u-Zn-A l mainly C u-Zn next nearest-neighbour pairs control the change in Mr.