Microstructure and creep properties of a cast Mg-1.7%wt rare earth-0.3%wt Mn alloy

A study has been undertaken to reveal the creep properties of an experimental magnesium alloy, Mg-1.7RE-0.3Mn, and its microstructure after creep. Transmission electron microscopy examinations on the samples over aged during creep showed that extensive precipitation of Mg₁₂RE type intermetallics took place on dislocations in the form of long single rows. Other precipitates of Mg₁₂RE with lozenge morphology were observed to be distributed more uniformly inside the grains. Precipitates types have been identified via X-ray and electron diffraction, and microanalysis techniques. The relatively low creep rate compared to the commercial magnesium alloys was measured. A high value of activation energy, 240 kJ/mol, was calculated. The creep resistance and the activation energy of the alloy were discussed in terms of microstructural observations.