Microstructure and mechanical behaviors of the ultrafine grained AA7075/B4C composites synthesized via one-step consolidation

We report on an investigation of the influence of sintering temperature on microstructure and mechanical behaviors of the Al matrix composites. In this paper, the ultrafine grained AA7075/B4C composites was synthesized via cryomilling and one-step consolidation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized for characterization of the grain size of the AA7075/B4C composites consolidated at various sintering temperatures. Our results indicated that the grain size increased gradually from ∼73.1 nm to ∼184.7 nm with the sintering temperature increasing from 350 °C to 450 °C. The formation of abnormal grain growth was observed in the AA7075/B4C composite consolidated at 500 °C B4C particles distributed homogenously, discretely and randomly in the Al matrix based on the observation in Field-emission scanning electron microscopy (FESEM). The porosities were found to decrease in the AA7075/B4C composites with the rising of sintering temperature. The Vickers hardness, compressive yield strength and fracture strength of the AA7075/B4C consolidated at 450 °C were 233 HV, 724.9 MPa and 834.5 MPa, respectively. The analysis of strengthening mechanisms revealed that increasing of sintering temperature resulted in the sacrifice of grain-boundary strengthening and dislocation strengthening.