不同铸造方法对7075铝合金热导率及力学性能的影响

采用金属型铸造、液态挤压铸造和半固态挤压铸造方法制备了7075铝合金,研究了不同铸造工艺对7075铝合金热导率与力学性能的影响。结果表明,金属型铸造晶粒粗大,产生枝晶偏析降低塑韧性,抗拉强度及伸长率最小,分别为121 MPa和2.78%,但晶粒粗大使热量传导路径宽,对电子散射几率小,电子的平均自由程较长,热导率相对较高,达到了139.67W/(m·K);液态挤压铸造晶粒细化,抗拉强度和伸长率分别为239MPa和5.75%,但晶粒细小且枝晶臂较多,对电子散射程度大,热导率最低,为120.94W/(m·K);半固态挤压铸造的晶粒致密细小且圆整,抗拉强度及伸长率最高分别达到248MPa和7.46%,且热导率为126.07W/(m·K)。

Effects of Different Casting Methods on Thermal Conductivity and Mechanical Properties of 7075 Aluminum Alloy

7075 aluminum alloy was prepared by permanent mold casting(PMC),liquid squeeze casting(LSC)and semi-solid squeeze casting(SSC)methods.The effects of different casting processes on the thermal conductivity and mechanical properties of 7075 aluminum alloy were investigated.The results indicate that the grains of the PMC are coarse,and dendrite segregation occurs to reduce the plastic toughness.The tensile strength and elongation are 121 MPa and 2.78%,respectively.However,the coarse grains exhibit a wide heat conduction path,lower electron scattering probability,long mean free path and relatively high thermal conductivity,which reaches139.67 W/(m·K).The tensile strength and elongation of the LSC refined grains are 239 MPa and 5.75%,respectively,while fine grains and more dendritic arms lead to the higher electronscattering,with the lowest thermal conductivity,which is 120.94 W/(m·K).SSC grains are compact fine and round,with the highest tensile strength and elongation of 248 MPa and 7.46%,respectively,and the thermal conductivity is 126.07 W/(m·K).