Zn和Mg质量比对7055铝合金淬火敏感性的影响

摘要

通过测定时效曲线,结合金相显微镜和透射电镜等组织观察以及DSC分析,研究Zn和Mg质量比(4.10和4.67)对7055铝合金淬火敏感性的影响.结果表明:在120℃时效时,合金的淬火敏感性随着时效时间的延长而降低,而Zn和Mg质量比低的合金比Zn和Mg质量比高的合金的淬火敏感性高7％～11％:空气淬火时,Zn和Mg质量比低合金的再结晶晶粒内析出了较多粗大的η(MgZn2)平衡相,因而减少了过饱和固溶体中溶质原子的数量,降低合金的时效强化效果,提高合金的淬火敏感性:然而,Zn和Mg质量比高的合金在空气淬火过程中析出的η相较Zn和Mg质量比低的合金少,且在局部形成了S(A12CuMg)相.%The effect of Zn and Mg mass ratio (4.1 and 4.67) on the quench sensitivity of aluminum alloy 7055 was studied by means of ageing curve testing, optical microscopy (OM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results show that the quench sensitivity decreases with the increase of ageing time at 120 ℃, and that of the alloy with lower Zn and Mg mass ratio is 7%-ll% higher. There are more coarse η(MgZn2) equilibrium phases in the recrystallized grains of the alloy with lower Zn and Mg mass ratio. Consequently, fewer solute atoms are obtained from the supersaturated solid solution, and lower ageing hardening effect is achieved, which leads to the increase of quench sensitivity. In the alloy with higher Zn and Mg mass ratio, fewer η phases are precipitated during air-quenching, and S(Al2CuMg) phase is observed locally.