[Order-hardening in equiatmic alloy CuPt (author's transl)]

The order-hardening and its modes of equiatomic alloy CuPt were investigated by means of hardness test, X-ray diffraction and optical microscopic observations. The important results obtained are as follows; (1) Two different modes of order-hardening are recognized, namely at the temperature ranges of 400 degrees C-550 degrees C and 600 degrees C-700 degrees C. (2) The activation energies for order-hardening at lower and higher temperatures are 19.3 and 31.1 kcal/mol, respectively. The former corresponds to the migration and the annihilation of quenched-in excess vacancies, the latter corresponding to the growth of ordered domain. (3) Heterogeneous ordering along the grain boundary at lower temperature and homogeneous ordering within the grain at higher temperature are the dominant reaction for hardening. But the ordering is achieved by the nucleation-and-growth process at all temperature.