A novel method for the fabrication of Al-matrix nanocomposites reinforced by mono-dispersed TiAl3 intermetallic via a three-step process of cold-roll bonding, heat-treatment and accumulative roll bonding

Abstract

A novel method to fabricate aluminum metal-matrix composites reinforced by mono-dispersed TiAl3 intermetallic particles, by cold-roll bonding, heat treatment, followed by accumulative roll bonding (ARB), is demonstrated. Roll bonding of 1100-Al sheets inserted with Ti powder was carried out at room temperature with 50% thickness reduction. Complete conversion of the initial Ti particles into TiAl3 intermetallic was achieved by a post-rolling annealing treatment at 590 °C for 2 h, which results in the formation of coarse TiAl3 particles along the interface of the original 1100-Al sheets. Subsequent ARB process was applied to break up and disperse the TiAl3 phase, and after 5 cycles of ARB, an aluminum-matrix composite with mono-dispersed TiAl3 particles of submicron sizes was achieved. The Al matrix also undergoes dynamic recrystallization during the ARB process to result in a fine-grained microstructure (size less than 500 nm). The hardness, tensile strength and elongation of the Al/TiAl3 composite were found to increase with the number of ARB cycles. The tensile strength of the Al/TiAl3 composite after the 5th cycle reaches 400 MPa, which is significantly higher than the 300 MPa of monolithic 1100-Al processed in the same way. The tensile elongation of the Al/TiAl3 composite after 5 cycles of ARB exhibits a good value of ∼8%, with a ductile fracture mode. This is the first successful attempt to achieve Al-matrix nanocomposites reinforced by mono-dispersed TiAl3 intermetallic based on an ARB method.