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Abstract
The microstructure and mechanical properties of AZ91 magnesium alloy with composition Mg – 8.8%Al – 0.78%Zn (wt-%) has been investigated to assess the possibility of improving the properties through precipitation hardening. Initially, both solutionising temperature and soaking time were optimised at 693 K and 8 h respectively. After solutionising, the AZ91 samples were subjected to artificial aging at 423 K, 448 K, and 473 K for a period of 12 to 120 h. The sample age hardened at 473 K attained peak hardness after a shorter time than the other two aging temperatures. Structural changes and corresponding mechanical properties were studied. As cast, solutionised and age hardened AZ91 samples were also subjected to corrosion studies to observe potentiodynamic polarisation behaviour. Fine precipitate formation throughout the matrix was observed following solutionising and then artificial aging. Microstructural modifications improved both tensile strength and elongation, however, the corrosion rate was not significantly influenced.