Ag对Al-5.3Cu-0.8Mg合金铸态组织与时效硬化行为的影响

Effects of Ag on age-hardening behavior and as-cast structure of Al-5.3Cu-0.8Mg alloy

采用金相显微分析技术、布氏硬度、XRD分析、室温与高温拉伸性能测试等方法,研究了Ag对Al-5.3Cu-0.8Mg合金铸态组织与时效硬化行为的影响。研究表明:Ag对合金铸态组织有细化作用,随着Ag含量的增加,枝晶得到细化;Ag添加缩短了合金的峰时效时间,其原因在于Ag原子提高了合金析出相的形核速率,进而加速了析出相的形成;随着Ag含量的增加,合金的硬度先增加后降低,含0.8%Ag的合金峰时效硬度最大;适量的Ag可以促进合金中Ω相的形成,过量的Ag将会抑制Ω相的形成;随着Ag含量的增加,合金的强度和热稳定性先升高后降低,当Ag含量为0.8%时,其强度和热稳定性均达到峰值;Ag提高合金强度与热稳定性的原因在于析出了热稳定性和强化作用比θ'、S'相更强的Ω相。

Effects of Ag on age-hardening behavior and as-cast structure of Al-5. 3Cu-0. 8Mg alloy were studied by means of metallographic analysis,XRD,hardness and tensile tests at room and elevated temperatures. The results show that Ag has refining effect on the as-cast structure,the dendrite crystal can be refined with the increase of Ag content. The peak-aging time of the alloys is shortened due to the addition of Ag,in which the Ag atom can increase the nucleation rate of precipitation and then speed up the formation of precipitation. The alloy hardness increases first and then decreases with the increase of Ag content,and the maximum peak-aging hardness is obtained for the alloy with 0. 8% Ag. Moderate Ag in the alloy improves the formation of Ω phase while the excess Ag restrains the formation of Ω phase.With the increase of Ag content,the strength and thermo-stability of the alloys increase first and then decrease,and reach the peak value when Ag content is 0. 8%. The improvement of the strength and thermo-stability of the alloys with Ag owes to the precipitation of Ωphase,which has greater influence on the strengthening and thermo-stability than θ＇ and S＇ phase.