The effect of heating rate and neutron irradiation on the specific heat behavior of a Cu-16.8 at. % A1 and A Cu-17.2 AT. % Ga solid solution

Abstract

The effect of heating rate on the specific heat behavior of binary solid solutions of copper containing 16.8 at.% Al and 17.2 at.% Ga in the range 40–700°C has been investigated. Also the effect of prior neutron irradiation on the spécifie heat behavior of the Cu-Al alloy was studied. The specific heats were measured with a dynamic adiabatic calorimeter. An anomalous behavior in the specific heat is observed in both solid solutions which is explained in a consistent manner based on the presence of short-range order. The initial slow cooling at approximately 1 2 °C/ min from above about 330°C leaves the alloys prior to reheating with short-range order present. Upon reheating the kinetics of disordering are such that disordering does not begin until about 200°C. The specific heat then shows an anomalous rise of about 7 per cent, then decreases slightly around 300°C. From about 300°C to 700°C the heating rates employed ( 1 2−7 °C/ min ) are low enough to allow instantaneous equilibrium to be established. The specific heats remain anomalously high at least to 700°C. The specific heat curves in the region from 200 to 300°C shift to higher temperatures with increased heating rate. Neutron irradiation at 100°C after slow cooling increases the amount of short-range order present and also introduces excess vacancies. The additional short-range order causes an increase in the specific heat curve as compared to just slow cooling, since more order is destroyed. Due mainly to the excess vacancies the anomalous behavior is observed at lower temperatures than for just slow cooling.