Microstructure and mechanical properties of brass/Mo composites processed via pressureless and spark plasma sintering

Abstract

Brass/molybdenum composites containing 30, 70 and 85 wt% Mo were synthesized by mechanical milling and densification of the brass/Mo powder mixtures. The milled powders were separately consolidated by spark plasma and pressureless sintering processes. The pressureless sintered samples were cold compacted under 300, 450 and 600 MPa before sintering. The results showed that by increasing the cold pressure up to 600 MPa, the relative density of the sintered samples with 70 and 85 wt% Mo were increased. However, the highest relative density of the brass-30 wt% Mo composites was achieved for the samples which were cold compacted under 450 MPa before sintering. The microstructural observations by scanning electron microscopy and energy dispersive spectroscopy analyses revealed that the distribution of Mo particles within the brass matrix of brass-30 wt% Mo composites was not as fine as the other samples. According to the results, the relative density and hardness of the spark plasma sintered samples was higher than that of the pressureless sintered ones. Moreover, increasing the volume percent of molybdenum has led to decreasing the relative density of the spark plasma sintered samples. The flexural strength of the spark plasma sintered composites with 30, 70 and 85 wt% Mo were 397, 376 and 114 MPa, respectively.