Deformation and Recrystallization of Alloys containing Two Phases

Abstract

Using mainly silver-magnesium alloys, the deformation of the phases was determined from observations of slip lines and recrystallization behaviour. The relative deformation of the two phases is influenced both by the total deformation of the alloy and by the volume fractions of the phases. When very little of the hard β phase is present most of the deformation occurs in the soft α crystals and there is additional flow of the matrix around the hard particles. If the proportion of the β phase is not greater than 30 per cent. by volume the soft α deforms more than the β for reductions of up to 60 per cent., but for heavier reductions the two phases deform more uniformly. When both phases are present in about equal proportions they deform to the same extent. The recrystallization behaviour of the phases in a duplex alloy is affected by the state of order of the phases, and by precipitation occurring in one of the phases on annealing the deformed alloy. Experiments were designed to show the influence of various factors. An alloy that is ordered before deformation recrystallizes at a lower temperature than an alloy disordered before deformation. It is shown that this behaviour is not due to a difference in work hardening characteristics. On annealing silver-magnesium and copper-zinc alloys quenched before deformation, precipitation of α occurs in the β crystals and the recrystallization temperature of the β is higher in these alloys than in slowly cooled alloys. It is shown that precipitation relieves internal stresses in the deformed matrix and thus causes the Increase in recrystallization temperature. The general case of recrystallization of the phases in slowly cooled and quenched silver-magnesium alloys is interpreted in terms of these results. The inhomogeneity of deformation of the phases is indicated by their mode of recrystallization.