Towards revealing the relationship between deformation twin and fatigue crack initiation in a rolled magnesium alloy

Abstract

Deformation twins usually play a crucial role in plastic deformation and undoubtedly influence the microstructural evolution and fatigue behavior of magnesium and its alloys. In the present work, an investigation focusing on the fatigue behavior of a rolled magnesium alloy has been conducted by a combination of scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) observations. The Schmid factor analysis is also carried out to evaluate the dislocation activation. The experimental results show that accompanying the cyclic deformation, 101¯2 twinning and detwinning dominate the fatigue deformation process and the residual 101¯2 twins increase with the number of fatigue cycles. The cracks prefer to initiate and propagate along 101¯2 twinning boundaries and slip bands. In addition, a large number of remarkable extrusions are also found within the twinned areas. Accordingly, the possible underlying mechanisms behind such phenomena are proposed and discussed. These findings are expected to provide an insight into understanding the relationship between microstructural feature and fatigue behavior in magnesium and other hexagonal close-packed metals.