INFLUENCE OF SHORT-RANGE DISORDER ON THE MARTENSITIC-TRANSFORMATION IN CU-ZN AND CU-ZN-AL ALLOYS

The transformation temperature, Ms in CuZn and CuZnAl alloys is changed by quenching from temperatures, TQ > Ms. In CuZn the quench from TQ leads to an increase in Ms, whereas in CuZnAl, Ms 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 CuZn nearest-neighbour pairs increase Ms, whereas in CuZnAl mainly CuZn next-nearest-neighbour pairs control the change in Ms. © 1979.