The role of aluminum oxide particulate reinforcements on cyclic fatigue and final fracture behavior of a novel magnesium alloy

In this research paper, the microstructure, hardness, tensile properties, tensile fracture, cyclic stress amplitude fatigue response and final fracture behavior of a novel magnesium alloy, denoted as AZ(12)1, discontinuously reinforced with nano-particulates of aluminum oxide (Al2O3) is neatly presented and convincingly discussed. The matrix alloy, which had three weight percent more aluminum than the monolithic counterpart (AZ91), was produced by solidification processing followed by hot extrusion. Properties spanning microhardness, tensile, high cycle fatigue and fracture behavior of the discontinuously reinforced magnesium alloy (AZ(12)1) are compared with the unreinforced monolithic alloy (AZ91). The elastic modulus, yield strength, tensile strength of the reinforced magnesium alloy is marginally higher than the unreinforced counterpart. The ductility quantified by elongation to failure over 0.5 in. (12.7 mm) gage length of the test specimen and reduction in specimen cross-section area of the composite was noticeably lower than the monolithic counterpart. At the fine microscopic level both tensile fracture and cyclic fatigue fracture of the composite revealed fewer features reminiscent of the occurrence of locally ductile mechanisms when compared with the monolithic counterpart. Over a range of maximum stress and at two different load ratios the cyclic fatigue resistance of the composite was noticeably inferior to the monolithic counterpart. The key mechanisms responsible for the inferior cyclic fatigue life and fracture resistance of the composite microstructure are elucidated.