Effect of grain size on flow stress of textured Zn alloy

Abstract

The mechanical properties of a commercial rolled Zn–0·1Al–0·05Mg alloy have been investigated at room temperature. A range of grain sizes was established using grain growth at elevated temperature, and it has been shown that this changed neither the shape of the grain size distribution nor the texture. The mechanical tests were performed as a function of strain rate: specimens were cut either parallel or perpendicular to the initial rolling direction. The thickness of the specimens was also varied so that the effect of the relationship of grain size to specimen thickness could be determined. The data from the tests have been compared with the predictions of the Hall–Petch equation. The equation was found to be obeyed only above a critical grain size. The behaviour of specimens with intermediate grain sizes depends on the direction of loading: longitudinally strained specimens deform initially by slip alone, while transverse specimens deform by a process which involves twinning at all strains. At large grain sizes, twinning is involved throughout the deformation of all specimens.