Mechanical and Wear Behavior of Al-Si5Cu3/ZrB2 In-Situ Reinforced Metal Matrix Composite

Abstract

In this study, the in-situ ZrB₂/Al-Si5Cu3 aluminum alloy composites were fabricated through the salt-melt reaction route with different weight fractions of ZrB₂ reinforcements, i.e., 2.5%, 5%, and 7.5%. The composites were tested for their density, hardness, tensile strength, flexural strength, impact strength, and wear properties. The influence of reinforcement on the properties was studied concerning the wt.% of reinforcement. The increase in density of composites compared to the matrix material confirms the formation of the in-situ reinforcement phase. The microstructure showed a desirable distribution of reinforced particles over the matrix at all weight fractions of the reinforcements in the composites. The ZrB₂ particles formed in the matrix have particle sizes in the range from 255 nm to 955 nm and the grain size has been reduced from 242 microns to 110 microns as the result of particle-induced solidification. The hardness of the composites containing ZrB₂ reinforcements of 2.5, 5, and 7.5 wt.% showed improvement by 8%, 17.5%, and 34% respectively compared to the parent alloy. There is an improvement in the tensile strength and elongation for the wt.% of ZrB₂ up to 5 wt.%, from 115 MPa to 183 MPa, after which, there was a drop in the tensile strength. The detailed analysis of tensile fractography shows that the agglomerated ZrB₂ reinforced particles at higher weight fractions lead to a decrease in strength. The results of flexural strength also affirm the strength of 5 wt.% ZrB₂/Al-Si5Cu3 increased from the matrix material’s flexural strength of 337 MPa to 672 MPa. The wear study shows that the composite with 7.5 wt.% ZrB₂ possesses a higher wear resistance. However, the impact strength did not show any differences in the weight % of reinforcement.