The Influence of Testing Temperature and Thermal History on the Intergranular Embrittlement and Penetration of Aluminium by Liquid Gallium

Abstract

Embrittlement and/or penetration of aluminium grain boundaries by liquid gallium have been investigated by a radiotracer technique and measurement of mechanical properties. A distinction is made between penetration without external stress and the embrittlement itself. However, the results show that a description of grain-boundary embrittlement must take into account the preliminary step of intergranular penetration by gallium. Moreover, two stages must be distinguished in the penetration of gallium; the driving force of the first stage seems to be a strong interaction between gallium and the grain boundaries. This interaction is usually described as intergranular adsorption. A general scheme for aluminium grain-boundary embrittlement and/or penetration is proposed. Some observations on the microstructure of the grain-boundary surfaces separated by liquid gallium are also reported. This technique of intergranular embrittlement by liquid gallium provides a new means of examining the structure of intergranular surfaces and augments the micro-fractography technique used for body-centred cubic metals.