Synthesis, microstructure and mechanical properties of bronze-molybdenum composites processed via LPS and SPS methods

In this work, synthesis, densification and properties of bronze-70 wt% Mo and bronze-30 wt% Mo composite powders were investigated. The composite powders were prepared by mechanical milling of bronze-Mo powder mixtures for 16 h. The results of cold compressibility investigations showed that Heckel and Ge equations provided the best fit scenario for bronze-70 wt% Mo and bronze-30 wt% Mo, respectively. The composite powders were consolidated via pressureless and spark plasma sintering processes. The relative densities of spark plasma sintered samples with 30 and 70 wt% molybdenum were about 98%. However, the relative density of bronze-70 wt% Mo and bronze-30 wt% Mo pressureless sintered samples were 97.1 and 94.3%, respectively. The scanning electron microscopy observations revealed that the size and dispersion of Mo particles within the bronze matrix in the pressureless sintered samples was completely different from that of the spark plasma sintered ones. Furthermore, it was found that in spite of nearly close relative densities, the hardness and flexural strength of the spark plasma sintered samples were higher than that of the pressureless sintered ones which was due to different shape, size and dispersion of the Mo particles within the matrix phase in the different samples. According to the results, the preferred densification process was SPS method.