Grain size effects on deformation twinning in an extruded magnesium alloy tested in compression

Ambient temperature compression tests with concurrent acoustic emission (AE) measurements have been performed on a hydrostatically extruded, fine-grained, round bar of alloy AZ31 parallel to the extrusion axis. A multiple increase in the AE count rates to peak intensities was detected with increasing strain. An analysis of the samples tested to specific values of strain using electron backscattering diffraction revealed that (10–12) twins first appear in large grains and that only with increasing strain do smaller grains tend to twin.