Investigation on the effect of reinforcement compositions on the properties of Aluminum LM 25/h-BN/B 4 C hybrid composites

Abstract

This study investigates the effect of the compositions of hexagonal boron nitride (h-BN) and boron carbide (B4C) reinforcements on the properties of aluminum matrix composites (AMC). The compositions of both the reinforcements in the Aluminum LM 25(A 356) alloy metal matrix are varied from 0 to 10% by volume. Based on the mixture design of experiment, ten AMCs are fabricated with different reinforcement compositions by the stir casting process. The microstructure, density, porosity, and hardness of these AMCs are analyzed and compared with that of unreinforced base aluminum alloy to study the effects of reinforcement composition. Microstructure analysis revealed that the reinforcements were uniformly distributed in the matrix phase with minimal agglomeration for the composites with up to 6% reinforcements. The density was found to decrease with the increase in the reinforcements due to the presence of porosities in the matrix and the addition of low-density reinforcements. With the increase in the volume percentage of reinforcements in hybrid composites, there was an increase in hardness. BC10BN0 mono composites exhibited the highest hardness value of 78.8 BHN due to the presence of hard B4C ceramic particles, whereas BC10BN0 demonstrated the lowest hardness of 57.13 BHN because of the h-BN particles having lower hardness than B4C particles. Among the hybrid composites, BC5BN5 resulted in the highest hardness, which was 26.3% higher than the base aluminum alloy. From the desirability analysis, 94.194% of LM 25, 2.389% of h-BN, and 3.417% of B4C were found to be the optimal conditions for minimizing porosity and maximizing hardness. The hybrid aluminum matrix composites developed in the present study can be utilized for automobile and aerospace applications.