ZA22/Al_2O_3短纤维复合材料高温拉伸行为的理论分析

THEORETICAL ANALYSES ON TENSILE STRENGTH OF ZA22/Al_2O_3 SHORT FIBER COMPOSITES AT ELEVATED TEMPERATURE

采用日本产ＡＧ－１０ＴＡ型电子万能试验机对挤压铸造ＺＡ２２／Ａｌ２Ｏ３短纤维复合材料的高温抗拉强度进行了测定，并用Ｆｒｉｅｎｄ修正的混合律模型对该试验结果进行了理论分析，结果表明ＺＡ２２／Ａｌ２Ｏ３短纤维复合材料及其基体的强度均随温度升高而下降，但ＺＡ２２合金基体的强度下降幅度更大。任一纤维体积分数的复合材料，均存在一临界转变温度Ｔｃｒｉｔ；超过该温度，复合材料强度大于基体强度。纤维体积分数越大，所需临界转变温度越低。在本试验中，Ｖｆ为１５％和２０％的复合材料的Ｔｃｒｉｔ分别为１２３℃和８７℃。任一温度下，复合材料均存在一临界纤维体积分数，超过该纤维体积分数，复合材料强度高于基体强度。温度越高，临界纤维体积分数越低。对ＺＡ２２／Ａｌ２Ｏ３短纤维复合材料来说，Ｆｒｉｅｎｄ模型中的经验参数Ｃ＊的取值随温度升高而降低。

The tensile strength of squeeze casting ZA22/Al 2O 3 short fiber composites at elevated temperature was measured with autograph AG 10TA universal testing machines made in Japan. The experimental results were analyzed by means of the rule of mixture (ROM) model modified by Friend. The results show that the tensile strength of ZA22 alloy and ZA22/Al 2O 3 short fiber composites decreases with the increasing temperature, but the decreasing rate of the tensile strength of ZA22 alloy is larger than that of ZA22/Al 2O 3 short fiber composites. There is a critical temperature T crit for any composites with a fiber volume fraction. The tensile strength of the composites is higher than that of matrix if the temperature is above T crit . The more the fiber volume fraction is, the lower the critical temperature T crit . T crit of the composites with 15% and 20% fiber volume fraction are 123℃ and 87℃, respectively. There is a critical fiber volume fraction V crit under a temperature. The tensile strength of the composites is higher than that of matrix if V f is above V crit . The higher the temperature, the lower the critical fiber volume fraction. For ZA22/Al 2O 3 short fiber composites, the value of the empirical parameter C * in Friend model decreases with the increasing temperature.