Effect of volume fraction on microstructure and wear behavior of dual-phase brass/W surface composites fabricated via friction stir processing

Abstract

The objective of this study is to fabricate brass matrix composites (BMCs) via friction stir processing (FSP) for enhancing the wear resistance of brass. The tungsten (W) particles ranging from 0 to 18 vol.% were reinforced in the brass (Cu-40Zn) matrix through FSP. The FSP derived exceptional homogeneous dispersion of W particles leaving no traces of agglomeration and isolation. The bonding between the interface and brass matrix was strong due to the absence of pores and undesirable compounds. Irrespective of the density gradient, FSP nullified the unfavorable effect on W dispersion in BMCs. The BMCs revealed fine-grained structures in the microstructural studies when compared to that of as-received brass, which reported an average grain size of 13 µm. Particularly, the BMC with 18 vol.% W particles showed higher reduction in the average grain size (4 µm), which was 70% less than that of as-received brass. Furthermore, the transmission electron microscopy studies recorded discontinuous dynamic recrystallization and dense dislocations with a density of 9.31  ×  108/mm near the stir zone. This led to an improvement in the hardness of BMCs. The BMC with 0 vol.% of W particles reported a hardness of 142 Hv whereas the BMC with 18 vol.% W particles revealed a hardness value of 165 Hv. Moreover, there was a proportional increase in hardness concerning the increase in W particles. The presence of W particles dipped the wear rate of BMCs during sliding tests and emanated smaller wear debris than the brass matrix. The wear rate was found to be 341  ×  10−5mm3/m at 0 vol.% of W particles whereas the wear rate was reduced to 185 × 10−5mm3/m at 18 vol.% of W particles. The W particles in BMCs were responsible to alter the adhesive wear into abrasive wear and upgraded the wear resistance of brass material.