Abstract
The present study was undertaken to investigate the role of matrix composition (pure Al vs experimental 6063 alloy) and heat treatment conditions on the tensile properties, and fracture behavior of Zr and Ti-containing Al-15vol% B4C metal matrix composites. While addition of transition elements such as Zr, Sc and Ti to Al alloys is known to enhance their high temperature performance, in the case of composites, the presence of the reinforcement may alter the strengthening kinetics in the composite material due to reinforcement/matrix interactions which could affect or hinder the properties otherwise expected from the matrix alloy. The study therefore focused on (i) a complete characterization of these composites, and (ii) an evaluation of their performance at elevated temperatures. Tensile tests performed on aged Metal Matrix Composites (MMCs) show that Zr (with or without Ti) resulted in a noticeable hardening due to the precipitation of Zr-rich phase. Precipitation of Zr-Ti compounds during aging contributed to the composite strength. Maximum strengthening was obtained from the 6063-based MMC due to the precipitation of Mg2Si phase particles. The addition of Zr and Ti resulted in the formation of protective layers around the B4C particles that were retained after fracture. The B4C fractured transgranularly without debonding from the matrix. Stacking faults were commonly observed in fractured Al 6063/B4C/15p composite samples.