The effect of sintering methods on the properties of B4C reinforced pre-alloyed Al composites produced by powder metallurgy method

In this study, effects of conventional, microwave and spark plasma sintering on microstructure, density, transverse rupture strength and hardness results in the production of Al-15Si-2,5Cu-0,5Mg/B4C composite material were investigated. Cold-pressed specimens were produced with uniaxial pressing technique by applying 620MPa pressure. Conventional and microwave sintering were performed at temperatures of 555, 580 and 605°C. Waiting times at sintering temperature were 60min for conventional sintering, without holding time (0min), 15, 30, 45 and 60min for microwave sintering. In the spark plasma sintering, 50MPa pressure and 450°C, 5min sintering parameters were used. Optical and scanning electron microscopes were used in microstructure analysis. Density measurement was made according to ASTM-B962-08. Hardness values were measured according to the Brinell. Transverse rupture strength tests were made in accordance with ASTM-B528-16. Differential thermal analysis was applied to Al-15Si-2,5Cu-0,5Mg powders. Elements and compounds in the microstructure of the Al-15Si-2,5Cu-0,5Mg sample were determined by X-ray diffraction. In the microstructure of the Al-15Si-2,5Cu-0,5Mg samples, elemental-Al, master alloy (Al-Si-Cu-Mg), primary-Si and θ(CuAl2), β(Mg2Si), γ(Al2CuMg) secondary phases were determined. The amount of pores increased with increasing reinforcement ratio. In conventional and microwave sintering methods, the optimum sintering temperature was determined as 555°C. Density over 96% was obtained in samples produced by spark plasma sintering. According to the hardness and transverse rupture strength results, it was determined that the samples produced without holding time at the sintering temperature give optimum values in microwave sintering.