The microstructures and the dislocation arrangements in die cast Mg alloy as well as the stressed alloys were investigated by using transmission electron microscopy, high-resolution transmission electron microscopy and energy dispersive X-ray analysis. Besides the dominant α-Mg and β-Mg17Al12 phases, Al8Mn5 and Mg5Al phases were also found and studied in the alloy. Dislocation pile-ups were found in the stressed AZ91D alloys for the first time. They were confined in the slip planes and piled up against the grain boundaries. The dislocation pile-ups increased with deformation to about 2.1% and then remained almost identical even when deformed to a higher degree. The dislocations pile-ups in the AZ91D alloy were found to be beneficial for a resistance to stress corrosion cracking. Dislocation networks were found to increase with deformation in all cases. Dislocation networks were also found in the β-Mg17Al12 phase as well as in the matrix in the deformed AZ91D alloys.

Microstructures and Dislocations in Stressed AZ91D Magnesium Alloys. R.M.Wang, A.Eliezer, E.Gutman: Materials Science and Engineering A, 2003, 344[1-2], 279-87