EFFECT OF COOLING RATE ON STRESS-STRAIN BEHAVIOUR AND MICROSTRUCTURE OF A CU- ZN- SN ALLOY (original) (raw)
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IOP Conference Series: Materials Science and Engineering
Common material for bullet shell is cartridge brass which contains 26-32 wt. % Zn. In the deep drawing process, problems are typically found, such as cracking and tearing, due to low ductility. Therefore, manganese is added to cartridge brass to increase its ductility. In this study, Cu-28Zn alloy with addition of 3.2 wt. % Mn was fabricated by gravity casting. As cast samples were homogenized at 800 °C for 2 hours. Afterwards, the specimens were cold-rolled with deformation of 20, 40, and 70 %. The 70 % cold-rolled samples were subsequently annealed at 350, 400, and 450 ℃ for 15 minutes. Samples underwent characterizations by microstructure analysis using optical microscope and Scanning Electron Microscope (SEM)-Energy Dispersive Spectroscopy (EDS), and Vickers microhardness testing. The results showed that higher degree of deformation led to more elongated grains with increasing values of L/D ratio, and higher hardness. Annealing at 350 ℃ for 15 min did not change the deformed microstructures which indicated the stage of recovery and stress relieve. Meanwhile, higher annealing temperatures of 400 and 450 ℃ led to recrystallization and grain growth, respectively. Hardness declined with the increase in annealing temperature. Mn increases the hardness and recrystallization temperature.
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Advances in Materials Science and Engineering, 2016
Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing technique. The influence of densifying on the properties of the hot pressed materials was investigated. The properties, such as the hardness, compressive strength, and wear resistance of these materials, were determined. The hot pressed Cu-Sn specimens included intermetallic/phases, which were homogeneously distributed. The presence of graphite improved the wear resistance of Cu-Sn alloys three times. Similarly, the presence of lead improved the densification parameter of Cu-Sn alloys three times. There was no significant difference in the mechanical behavior associated with the addition of Pb to the Cu-Sn alloys, although Cu-Pb alloys showed considerably higher ultimate strength and higher elongation. The Cu-Sn-C alloys had lower strength compared with those of Cu-Sn alloys. Evidence of severe melting spots was noticed in the higher magnifications of the compression fracture surface of 85% Cu-10% Sn-5% C and 80% Cu-10% Sn-10% Pb alloys. This was explained by the release of load at the final event of the fracture limited area.