搅拌时间对半固态过共晶铝合金坯料制备的影响

Effect of Stirring Time on Preparation of Semisolid Hypereutectic Aluminum Alloy Billet

过共晶Al-Si合金因其良好的耐磨性被广泛应用于航空、汽车等场合,主要是作为发动机活塞的原材料。但是,由于过共晶Al-Si合金的微观组织中存在复杂、大块的初生硅,合金的基体组织被破坏,材料的力学性能受到严重的影响。机械搅拌工艺可以细化过共晶Al-Si合金的初生硅组织,因此研究了搅拌时间对半固态铝合金坯料微观组织及力学性能的影响。为了更好地研究搅拌时间的影响,首先固定搅拌温度为650℃,搅拌速度为300 r/min;其次改变搅拌时间来制备半固态过共晶铝合金坯料。借助金相显微镜、布氏硬度机等手段对该坯料进行实验测试,观察其微观组织和表面布氏硬度,综合考虑其性能来寻求最佳搅拌时间工艺参数的取值范围。实验结果表明:在搅拌温度为650℃和搅拌速度300 r/min的条件下,搅拌时间20 min时,半固态过共晶铝合金的布氏硬度达到峰值,其值为87.43 HB,相比未经搅拌的提高了17.78%,微观组织中初生硅的尺寸变得较小且分布较为均匀。

Hypereutectic Al-Si alloy is widely used in aviation,automobile and other occasions because of its good wear resistance,mainly as the raw material of engine piston.However,due to the presence of complex bulk primary silicon in the microstructure of the hypereutectic Al-Si alloy,the matrix structure of the alloy is destroyed,and the mechanical properties of the material are seriously affected.Mechanical stirring process can refine the primary silicon microstructure of hypereutectic Al-Si alloy.The effect of stirring time on the microstructure and mechanical properties of semi-solid aluminum alloy billet was studied.In order to better study the effect of stirring time,firstly,the stirring temperature was fixed at 650℃ and the stirring speed was set at 300 r/min.Then,the semi-solid hypereutectic aluminum alloy billet was prepared by changing the stirring time.By means of metallographic microscope and Brinell hardness machine,the billet was tested to observe its microstructure and surface Brinell hardness,and to find the best range of stirring time parameters by considering its properties.The experimental results show that the brinell hardness of semi-solid hypereutectic aluminum alloy reaches the peak value of 87.43 HB when the stirring temperature is 650℃ and the stirring speed is 300 r/min,and the stirring time is 20 min,which is 17.78%higher than that without stirring.The size of primary silicon in the microstructure becomes smaller and more uniform.