MECHANICAL STRENGTH CHARACTERS OF ZL108 ALLOY COMPOSITES REINFORCED BY Al₂O₃-SiO₂ FIBRE

Using low cost Al₂O₃-SiO₂ fibre as reinforced phase.ZL108 alloy composites were made by squeeze casting. The composites and ZL108 alloy were accelerated ageing at different temperatures.and then examined by compression test. The analysis from DSC,EPMA and TEM suggests that the reason why after the accelerated ageing at 488K for 30min (T6).the compression proof stress of the composite with 20 V_f% fibre below 573K was lower than that of ZL108 alloy is the reaction of Mg in the matrix and Al₂O₃-SiO₂ fibre,which formed MgAl₂O₄, consumed lot of Mg in the matrix.and led to the poor ageing hardness and low compression proof stress. It is proposed that after annealing at 623K for 720 hours,the compression proof stress of the composite being much higher than that of ZL108 alloy is because ZL108 alloy produced over ageing at these temperatures. Therefore the effect of fibre reinforcement on the tomposite was significant. At high temperature of 673K.the proof stress of the composite with 20 V_f% fibre was about twice as high as that of ZL108 alloy. At all temperatures,the proof stress of composite with 5 V_f% fibre is lower than that of composite with 20 V_f%.