Effect of twin boundaries on indentation behavior of magnesium alloys

Abstract

The effect of twin boundaries on indentation behavior was investigated in Mg-0.3 at.%X (X = Al, Li, Y and Zn) binary alloys containing preexisting {101¯2} deformation twins. These alloys exhibited the highest hardness values reported among both fine- and coarse-grained alloys studied in the literature, irrespective of the alloying elements present. The activation volumes for plastic deformation were found to lie between 18b3 and 60b3, consistent with a rate-controlling mechanism of dislocation slip. These activation volumes were similar to previously reported results for alloys devoid of twins prior to testing, suggesting that although twin boundaries do not affect the dominant deformation mechanism, they lead to an increase in hardness. On the other hand, the activation volumes obtained from indentation tests were different from those obtained by uniaxial compression tests in samples without pre-existing twins, due to the occurrence of microstructural evolution, i.e., deformation twin formation, during plastic deformation.