Nanostructured Mg–5%Al–x%Nd alloys

Nanocrystalline Mg–5%Al–x%Nd (x=0.5, 1 and 5 wt.%) powders of crystalline size about 23 nm were prepared by mechanical alloying. The mechanically alloyed powders were consolidated using conventional pressing, sintering and extrusion processes. Microstructural characterisation of the consolidated specimens revealed an average crystalline size of about 90 nm. Metastable MgNd phase was found in the milled samples and this transformed into Mg12Nd on sintering. The complete transformation of MgNd into Mg12Nd was dependent upon the duration of milling and the sintering temperature. Mechanical properties in terms of 0.2% yield stress and ductility were found to increase after mechanical alloying. The increase in yield stress and ultimate tensile stress was attributed to the presence of metastable MgNd phase as well as to the reduction in grain size. The decomposition of MgNd may have contributed to the lowering of strength and enhancement of ductility in samples milled for the longest period and sintered at the highest temperature.