Influence of multi-pass FSP on the microstructure, mechanical properties and tribological characterization of Al/B4C composite fabricated by accumulative roll bonding (ARB)

This paper aims to understand the impact of post-multi-pass friction stir processing (FSP) on the microstructure, mechanical, wear and fracture behaviors of the fabricated 10 cycle-accumulative roll bonded Al-2%B4C composites. The increase in the number of tool-passes directly improved homogeneity and fragmentation of B4C particles, microhardness, tensile strength (86.84-173.92 MPa) and fracture resilience of the Al-2%B4C composite. The tribological properties of the composite are improved with a rise in the number of tool passes. Wear rate, upper boundaries and mid-fluctuation lines of the friction coefficient decreased from 6.198 x 10(-5) to 1.095 x 10(-5) mm(3)/Nm, 0.56 to 0.19, and 0.31 to 0.11 respectively as the number of tool passes was varied between 1 and 8 passes. An increase in the sliding distance caused an overshoot of the complete waveform of friction coefficient to be above the mid-line of fluctuation due to the induced frictional/thermal input emanating from the prolonged surface-surface contact. Homogenous particle dispersion imposes abrasion wear mechanism on the composite. Ductile fracture is the predominant failure mode of the composites. Post-multi-pass friction stir processing of the accumulative roll bonded Al-2%B4C composite is an effective approach of achieving high performance in Al-B4C composite.