Utilizing Additive Friction Stir Processing to Fabricate B4C Reinforced Ti-6Al-4V Matrix Surface Composite: Microstructure Refinement and Enhancement in Mechanical Properties

Ti-6Al-4V/B4C surface composite, having uniform dispersion of reinforcement, was successfully fabricated via additive friction stir processing (AFSP) technique. The chemical reaction between B4C particles and Ti matrix resulted in the formation of intermetallics like TiBX and TiC. Optical microscopy, scanning electron microscopy, electron backscattered diffraction and X-ray diffraction were carried out to investigate the influence of FSP, B4C reinforcement and post-FSP heat treatment on microstructure evolution. Microhardness, Charpy impact and pin on disc wear tests were performed to examine mechanical and wear properties. Fully beta transformed microstructure composed of basket-weave lamellar alpha/beta together with the needle-like ultrafine martensite alpha ' was observed in FSPed stir zone. B4C particles brought about additional microstructure refinement by pinning prior beta grain boundaries (Zener pinning) and enhancing the nucleation rate (particle stimulated nucleation). Surface composites fabricated via AFSP exhibited higher hardness, wear-resistance and impact toughness compared to the base metal Ti-6Al-4V and FSPed Ti-6Al-4V. Graphic Abstract

Automated summary

Ti-6Al-4V/B4C surface composite was successfully fabricated via additive friction stir processing (AFSP) technique, with uniform dispersion of reinforcement. B4C particles reacted with the Ti matrix, forming intermetallics like TiBX and TiC, while also refining the microstructure through Zener pinning and particle-stimulated nucleation. Surface composites produced by AFSP exhibited improved hardness, wear-resistance, and impact toughness compared to base metal Ti-6Al-4V and FSPed Ti-6Al-4V.