Strengthening Effect of Y 2 O 3 on AZ92 Magnesium Alloy Using Stir Casting Process

Strengthening effect of Y2O3 on AZ92 magnesium alloy using stir casting process has been investigated. Nominal amounts of Y2O3 (0, 1, 1.5, 2, 2.5 and 3 in wt%) were added into the melt vortex in the form of preformed master powder (Mg–30 wt% Y2O3) to improve their wettability with molten AZ92 alloy. The results showed clearly that without Y2O3 addition, the microstructure of the investigated alloy is composed of α-Mg which appeared as coarse dendritic structure, divorced eutectic-containing massive β-Mg17Al12 phase and super-saturated α-Mg solid solution. With Y2O3 addition, the distribution of Y2O3 particles was found within the inter-dendritic regions of the primary α-Mg phase. At 2.5 wt% Y2O3, a near uniform distribution of Y2O3 particles along the grain boundaries of AZ92 alloy matrix was successfully obtained. However, further addition resulted in agglomeration of Y2O3 particles at 3 wt% addition level. The average tensile strength of the investigated AZ92 alloy was increased from 169 MPa to 198 MPa without a significant reduction in its ductility at optimum addition of 2.5 wt% Y2O3. The fracture mechanism has been also investigated.