POSITRON-ANNIHILATION STUDY OF THE QUENCHED-IN VACANCIES IN CUZNAL ALLOYS

The excess vacancies in ternary CuZnAl and Ti-doped CuZnAl alloys quen ched from temperatures between 673 K and 1223 K, and the behaviour of the quenched-in vacancies on postquench aging in martensite phase have been studied by Doppler broadening measurements. It has been found th at adding Ti to the alloys results in the formation of vacancy-Ti solu te atom complexes which lowers the mobility of the vacancies. In the T i-free alloy, the prominent changes in the lineshape S-parameter durin g the early stage of martensite aging have evidenced the occurrence of vacancy migration to sinks, clustering or vacancy. related atomic dis tortion. The role of the vacancies in martensite stabilization has bee n discussed.