Role of powder preparation route on microstructure and mechanical properties of Al-TiB2 composites fabricated by accumulative roll bonding (ARB)

Accumulative roll bonding (ARB) was conducted up to seven cycles to fabricate Al-TiB2 particulate metal matrix composites. The reinforcing particles were prepared and used in three different processing conditions: as-received TiB2, mixed TiB2-Al and in-situ synthesized TiB2-Al. The mixed TiB2-Al powder was produced by milling of TiB2 with Al powder and in-situ synthesized TiB2-Al powder was prepared by mechanical alloying (MA) through inducing TiB2 particles in the Al with various composition of 10, 20 and 30 wt% Al. Transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to evaluate the microstructure of the produced composites. The composite obtained from the in-situ TiB2-Al powder showed the most uniform distribution of particles and exhibited the highest tensile strength of about 177 MPa in comparison with the composites reinforced with the as-received TiB2 (156 MPa) and mixed TiB2-Al powder (160 MPa). After seven ARB cycles, an ultra-fine grained structure with the average size of about 300 nm was obtained in the composite reinforced with in-situ TiB2-Al powder. The appearance of dimples in tensile fracture surfaces revealed a ductile-type fracture in the produced composites.