Study of the dislocation activity in a Mg–Y alloy by differential aperture X-ray microscopy

Highlights: • Subsurface grain structure in a Mg–Yalloy is measured by Laue microdiffraction. • Distribution of geometrically necessary dislocations is mapped in five grains. • Fraction of different types of dislocations is counted. • c + a dislocations make important contribution to the high ductility in Mg–Y. -- Abstract: Differential aperture X-ray microscopy (DAXM) was employed in this study to reveal the development of geometrically necessary dislocations (GNDs) when a Mg–5 wt% Y alloy is subjected to bending. The characters of the GNDs were determined from the streak direction of the diffraction peaks. Five grains were analyzed voxel by voxel for the GND content. Among those voxels with peak streaking, 77% contain basal or non-basal a GNDs, while the other 23% contain c + a GNDs. Those c + a dislocations were nucleated to accommodate local stress concentration. Even though c + a dislocations are less mobile, they make important contribution to the high ductility of Mg–Y alloys.