Influence of degree of deformation on anisotropy in mechanical properties in wrought magnesium alloy ZK60

A direct-chill (DC) cast magnesium alloys ZK60 has been forward-extruded at 300 deg. C in a single pass at two extrusion ratios (ER) 12 and 44, which correspond to a total degree of deformation (f) of 2.5 and 3.8, respectively. The as-extruded microstructure in both cases consists of two colonies of grain sizes, i.e. about 15 mu m and <5 mu m, and highly deformed original grains which have not recrystallized. The crystallographic texture at both extrusion ratios consists of a predominant component accompanied by a relatively weaker component in the extrusion direction. Although, the qualitative crystallographic texture at both extrusion ratios remains fairly similar, a higher extrusion ratio gives a relatively weaker basal texture. A relatively higher degree of DRX and much lesser volume fraction of coarse grains (>25 mu m) at higher extrusion ratios give significantly weaker strength differential effect (difference in tensile yield stress and compressive yield stress). (author)