CALORIMETRIC STUDY OF ISOTHERMAL RELAXATION IN A QUENCHED BETA-CU-ZN-AL ALLOY

The isothermal relaxation process in a beta-Cu-Zn-Al single crystal which follows quenches from different T(q) temperatures has been studied by means of an isothermal calorimetric technique at three T(a) temperatures. The relaxation has been attributed mainly to a reordering process which takes place through a vacancy mechanism. The dissipated energy during the process has been measured for the different T(a) and T(q) temperatures. We have found that the relaxation process is not of a single exponential type and that, in all cases, the recorded curves giving the dissipated thermal power, W(t), against time show long tails. The kinetics of the process have then been characterized by means of a relaxation time-tau, defined as the time at which the product tW(t) versus time shows a maximum. Assuming an Arrhenius law dependence of tau on T(a) and T(q), we have obtained effective activation energies of 0.76 +/- 0.03 eV and 0.43 +/- 0.03 eV for vacancy migration and formation respectively.