The Composition and Temperature Dependence on Some Properties of γ-phase in the Cu-Al System

Abstract

It is known that the compositional defects and thermal defects play a significant role in the high temperature properties of an intermetallic compound which exists over a wide range of composition. The present investigation was undertaken to study the effects of these defects on properties of the γ-phase in the Cu-Al system. The lattice parameter, absolute thermoelectric power, electrical resistivity and hardness were measured at various temperatures as a function of the composition. The results are summarized as follows:
(1) When the aluminum content was increased, the type of compositional defect of the γ-phase appeared to undergo a change from a substitutional to a vacancy type.
(2) The maximum of thermo-electromotive force was found to shift to the side of less aluminum content with increasing temperature. This shows that in the high temperature region the vacancy defect structure replaced the substitutional one at less aluminum content.
(3) The anomalies observed on the temperature dependence of lattice constant and resistivity took place owing to a clustering reaction of a large number of vacancies formed at elevated temperatures.
(4) The softening temperature of hardness was found to correspond well to the temperature of anomalies of resistivity and lattice constant in the compositional range studied.