Evaluation of the microstructure and wear behaviour of AA6063-B4C/TiB2 mono and hybrid composite layers produced by friction stir processing

Abstract

Friction stir processing (FSP) was used to produce mono and hybrid surface composite layers of aluminium matrix containing B4C and TiB2 particles. For this purpose the AA6063 was used as the base material. Different fractions of milled B4C and in situ TiB2–10 wt.%Al composite powder produced by mechanical alloying were incorporated into the matrix by FSP. The effect of different ratios of TiB2 and B4C reinforcing particles on the microstructure and wear resistance of surface layers was studied. Microstructural evaluation of the samples was conducted by optical microscopy and field emission scanning electron microscopy (FESEM) of the cross-sections of surface composite layers. Microhardness testing was conducted across the cross-sections of FSPed samples to obtain hardness profiles and pin on disk dry sliding wear test was conducted on FSPed samples. The results showed that the incorporation of B4C and TiB2 reinforcing particles to the surface increased the hardness and wear resistance of composite layers in comparison with FSPed AA6063 alloy. Moreover, 100%TiB2 surface composite layer exhibited the highest hardness and best wear behaviour compared to other fractions.