铜添加对近共晶Al-Si-xCu合金的微观组织和硬度的影响

摘要

研究铜含量对Al-Si-xCu (x=2％,3％,4％ and 5％)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℃铸造成湿砂模并固化,于500℃保温7h进行固溶处理后对样品进行水冷.随后于190℃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30 K/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℃的四元共晶相.%The influence of Cu content on the microstructure and hardness of near-entectic 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 ℃ and solidified.The solution treatment was performed at 500 ℃ for 7 h and then the specimens were cooled by water quenching.The samples were respectively aged at 190 ℃ 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 1decreases and the amount of these eutectic phases increases,quaternary eutectic phase with melting point of 507 ℃ forms when Cu content is more than 2％.