Abstract
The microstructure, tensile properties, cyclic stress amplitude fatigue response and final fracture behavior of a magnesium alloy, denoted as AZ31, discontinuously reinforced with nano-particulates of aluminum oxide and micron size nickel particles is presented and discussed. The tensile properties, high cycle fatigue and final fracture behavior of the discontinuously reinforced magnesium alloy are compared with the unreinforced counterpart (AZ31). The elastic modulus and yield strength of the dual particle reinforced magnesium alloy is marginally higher than of the unreinforced counterpart. However, the tensile strength of the composite is lower than the monolithic counterpart. The ductility quantified by elongation to failure over 0.5 inch (12.7 mm) gage length of the test specimen showed minimal difference while the reduction in specimen cross-section area of the composite is higher than that of the monolithic counterpart. At the microscopic level, cyclic fatigue fractures of both the composite and the monolithic alloy clearly revealed features indicative of the occurrence of locally ductile and brittle mechanisms. Over the range of maximum stress and at two different load ratios the cyclic fatigue resistance of the magnesium alloy composite is superior to the monolithic counterpart. The mechanisms responsible for improved cyclic fatigue life and resultant fracture behavior of the composite microstructure are highlighted.
Highlights
The sustaining need for materials that can be put to use in a spectrum of performance-critical and even non-performance critical applications coupled with their ability to be light in weight and offer beneficial mechanical properties spanning the domains of strength, ductility, toughness, fatigue resistance and even fracture behavior has become both essential and is required in order to facilitate their selection and use for a range of weight-critical applications
Of the reinforcements that have been tried and successfully used fine particulates of alumina or aluminum oxide (Al2O3) have engineered both attention and interest among researchers in the pursuit of developing magnesium-based composites [18]. It has been reported in the published literature that use of nano-sized reinforcements in a magnesium alloy metal matrix promises to exert a beneficial influence on ductility when compared one-on-one with the use of micron-size reinforcements [10,11]
No attempt was made in this study to determine the size of the reinforcing Al2O3 particulates dispersed in the magnesium alloy metal matrix
Summary
The sustaining need for materials that can be put to use in a spectrum of performance-critical and even non-performance critical applications coupled with their ability to be light in weight and offer beneficial mechanical properties spanning the domains of strength, ductility, toughness, fatigue resistance and even fracture behavior has become both essential and is required in order to facilitate their selection and use for a range of weight-critical applications. Of the reinforcements that have been tried and successfully used fine particulates of alumina or aluminum oxide (Al2O3) have engineered both attention and interest among researchers in the pursuit of developing magnesium-based composites [18] It has been reported in the published literature that use of nano-sized reinforcements in a magnesium alloy metal matrix promises to exert a beneficial influence on ductility when compared one-on-one with the use of micron-size reinforcements [10,11]. An examination of the fatigue fracture surfaces of the composite is made to understand and establish the specific role and influence of the dual phase reinforcement in synergism with processing and resultant microstructure on microscopic mechanisms governing cyclic deformation and fracture
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