Al2O3-SiO2纤维增强ZL108合金复合材料的强度特性

用低成本的Al₂O₃-SiO₂系纤维作为增强相,通过加压铸造法制作ZL108合金复合材料,并对该复合材料和ZL108合金进行不同温度下的时效处理和压缩试验。通过DSC、EPMA和TEM分析认为:经488K、0.5h时效处理(T6处理)的V_f 20%的复合材料在573K以下的压缩屈服强度低于ZL108合金,是由于基体中的Mg与Al₂O₃-SiO₂纤维在加压铸造过程中起化学反应而生成MgAl₂O₄,损耗了基体中的大量Mg,导致基体铝合金时效硬化效果很差,所以压缩屈服强度低下。623K、720h保温后的V_f 20%的复合材料的压缩屈服强度比ZL108合金要高得多,是由于在这种温度环境下对ZL108合金来说是过时效,所以纤维的增强怍用显得明显。在高温(673K)下V_f 20%的复合材料的屈服强度比ZL108台金高一倍左右。不论在什么温度场合下V_f5%的复合材料的屈服强度比V_f 20%的复合材料都低。

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 Vf% 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 Vf% fibre was about twice as high as that of ZL108 alloy. At all temperatures,the proof stress of composite with 5 Vf% fibre is lower than that of composite with 20 Vf%.