A particulate-hardened composite usually known as cermets with aluminum matrix and reinforced with ceramic particles from broken bottles was used to investigate the effect of ageing time on hardness and tensile streng...A particulate-hardened composite usually known as cermets with aluminum matrix and reinforced with ceramic particles from broken bottles was used to investigate the effect of ageing time on hardness and tensile strength. The samples used for the work were produced using stir-cast method and the samples were cast in metal moulds to improve on the surface finish and to obtain good cooling rate. The composite composition used was Al/0.5% glass particles. The samples were treated at 500?C and quenched in water at 65?C. They were then aged at various temperatures ranging from 150?C - 210?C. The result of the hardness test showed that within the range of the ageing time selected the hardness increased with the ageing for all the ageing temperatures used. Variations were observed but this is normal in ageing, particularly when coherent and incoherent precipitates are formed at a point in time, or when over-ageing occurs. The plot of the tensile strength tests and the hardness tests, with ageing time showed the trend as observed. The highest hardness value of 37.3 HRB occurred after 5 hours of ageing likewise the highest tensile strength value of 398.36 N/mm2 occurred after 5 hours of ageing at the same ageing temperature of 190?C. The aged composite showed improved hardness and tensile strength when compared to as-cast value of 23.7 HRB for hardness and 253.12 N/mm2 for tensile strength respectively.展开更多
文摘A particulate-hardened composite usually known as cermets with aluminum matrix and reinforced with ceramic particles from broken bottles was used to investigate the effect of ageing time on hardness and tensile strength. The samples used for the work were produced using stir-cast method and the samples were cast in metal moulds to improve on the surface finish and to obtain good cooling rate. The composite composition used was Al/0.5% glass particles. The samples were treated at 500?C and quenched in water at 65?C. They were then aged at various temperatures ranging from 150?C - 210?C. The result of the hardness test showed that within the range of the ageing time selected the hardness increased with the ageing for all the ageing temperatures used. Variations were observed but this is normal in ageing, particularly when coherent and incoherent precipitates are formed at a point in time, or when over-ageing occurs. The plot of the tensile strength tests and the hardness tests, with ageing time showed the trend as observed. The highest hardness value of 37.3 HRB occurred after 5 hours of ageing likewise the highest tensile strength value of 398.36 N/mm2 occurred after 5 hours of ageing at the same ageing temperature of 190?C. The aged composite showed improved hardness and tensile strength when compared to as-cast value of 23.7 HRB for hardness and 253.12 N/mm2 for tensile strength respectively.
