铸造高锌AlZnSiCu合金的力学性能与热导率研究

Study on Mechanical Properties and Thermal Conductivity of Cast HighZinc AlZnSiCu Alloy

以高锌AlZnSiCu合金为对象,通过控制Zn、Si元素,研究了重力铸造及高压铸造对其组织、力学性能和热导率的影响。结果表明:高压铸造相比重力铸造,α-Al晶粒明显细化且由柱状晶转化为等轴晶,晶界面积和初晶硅的尺寸减小,高压铸造下合金的强度和硬度较高,塑性及热导率低于重力铸造。2号、3号合金Zn含量的增加造成Al与Si的共晶反应减少,造成共晶硅减少,形状不规则的初晶硅增多,增加了组织的不均匀性。两种铸造方式下,3种合金的布氏硬度与热导率和伸长率变化趋势相反,其中2号合金的布氏硬度最高,分别为HBW127(重力铸造)、HBW170(高压铸造),相对于1号合金分别提升9.48%、30.76%,重力铸造下1号合金的热导率和伸长率最高,分别为103.73 W/(m·K)、1.7%。高压铸造下2、3号合金中固溶于α-Al中Zn元素较1号合金明显增多,晶界处的第二相数量增多,2号合金初晶硅尺寸较大,增加了电子传输过程中对自由电子的散射作用,使有效传输通道数量减少,降低合金传热能力。

The effects of gravity casting and high pressure casting on microstructure,mechanical properties and thermal conductivity of high zinc AlZnSiCu gold were studied by controlling Zn,Si and Sr elements.The results showed that compared with gravity casting,theα-Al grains were finer and transformed from columnar grain to equiaxed grain,the grain boundary area and primary silicon size decreased,and the strength and hardness of the alloy were higher under high pressure casting,and the plasticity and thermal conductivity of the alloy were lower than those of the gravity casting.The increase of the Zn content in No.2 and No.3 alloy resulted in less eutectic reaction between the Al and Si,less eutectic silicon,and more primary silicon with irregular shape,which increases the heterogeneity of the microstructure.Under the two casting methods,the brinell hardness and thermal conductivity and elongation of the three alloys had opposite trends.The Brinell hardness of the alloy 2 was the highest,which was HBW127(gravity casting)and HBW170(high pressure casting),which increased by 9.48%and 30.76%,respectively,compared with that of the alloy 1.The thermal conductivity and elongation of the alloy 1 were the highest under gravity casting,103.73W/m·k and 1.7%,respectively.Under high pressure casting,the number of the Zn elements dissolved in solidα-Al in the alloy 2 and 3 was significantly higher than that in the alloy 1,the number of second phase at grain boundary was increased,and the size of primary silicon in the alloy 2 was larger,which increases the scattering effect of free electrons during electron transmission,reduces the number of effective transmission channels and reduces the heat transfer capacity of the alloy 2.