铜添加对近共晶Al-Si-xCu合金的微观组织和硬度的影响

研究铜含量对Al-Si-xCu（x=2%,3%,4%and5%）合金的微观组织和硬度的影响。不同铜含量的铝合金经熔炼后于690°C铸造成湿砂模并固化,于500°C保温7h进行固溶处理后对样品进行水冷。随后于190°C进行时效处理,分别保温5,10和15h,研究时效时间对基体硬度的影响。采用差热分析法,在冷却速度30K/min下确定平衡相的转变温度,并研究铜含量对四元共晶合金的形成和α（Al）＋Si熔点的影响。结果表明,随着铜含量的增加,发生析出硬化从而导致基体硬度增加,α（Al）＋Si的熔点降低,共晶相的含量增加。当铜含量超过2%时,生成熔点为507°C的四元共晶相。

Influence of Cu addition on microstructure and hardness of near-eutectic Al-Si-xCu-alloys

The influence of Cu content on the microstructure and hardness of near-eutectic Al-Si-xCu (x = 2%, 3%, 4% and 5%) was investigated. After melting Al-based alloys with different Cu contents, alloys were cast in green sand molds at 690 °C and solidified. The solution treatment was performed at 500 °C for 7 h and then the specimens were cooled by water quenching. The samples were respectively aged at 190 °C for 5, 10 and 15 h to observe the effect of aging time on the hardness of matrix. Also differential thermal analysis was used to obtain the transition temperature of the equilibrium phases at cooling rate of 30 K/min and to determine the effect of Cu content on the formation of quaternary eutectic phases and the melting point of α(Al) + Si. The results show that as Cu content in the alloy increases, the hardness of matrix increases due to precipitation hardening, the melting point of α(Al) + Si decreases and the amount of these eutectic phases increases, quaternary eutectic phase with melting point of 507 °C forms when Cu content is more than 2%.