Investigation of microstructural, mechanical and tribological properties of Al356/3-9%ZrB2 composites produced by the stir casting process

Abstract

In this study, aluminum 356 cast alloy as the metal matrix was strengthened with various amounts (3, 6 and 9 weight percent) of ZrB2 reinforcement particles via stir casting process. The reinforcement particles were injected into the melt during the casting. Furthermore, precipitation hardening (T6) heat treatment was carried out on a series of the cast samples. Morphology and microstructure of the samples were studied by scanning electron microscopy (SEM), while elemental and phase analyses were conducted by EDS and XRD. Investigation of mechanical properties (wear resistance, tensile strength and micro-hardness) showed considerable improvement with increased content of the reinforcement material. In this regard, the tensile strength increases from 135 MPa in the matrix material to 248 MPa in the composite sample which contained 9% ZrB2. Furthermore, after a sliding distance of 2000 m in wear tests, the weight loss of the same two samples were 0.0604 and 0.0218 g, respectively. In this regard, T6 heat treatment significantly improved the mechanical and tribological properties of the composite such that an increase of ∼30% in tensile strength and a decrease of more than 60% in wear weight loss were achieved in the specimen with 9% ZrB2.