添加Cr和Yb对Al-Zn-Mg-xCu-Zr超强铝合金组织与性能的影响

Effect of Cr and Yb additions on microstructure and properties of Al-Zn-Mg-xCu-Zr alloy

通过力学拉伸、晶间腐蚀、剥落腐蚀与应力腐蚀测试,结合金相、扫描电镜以及透射电镜等分析手段,对比研究不同Cu质量分数（0.8%~2.2%）的Al-Zn-Mg-Cu-Zr和Al-Zn-Mg-Cu-Zr-Cr-Yb合金组织和性能的影响规律。研究结果表明：与Al-Zn-Mg-Cu-Zr合金相比,复合添加Cr和Yb的Al-Zn-Mg-Cu-Zr-Cr-Yb合金,可显著抑制再结晶和晶粒长大,充分保持基体的形变亚结构,提高合金的力学性能和抗腐蚀能力。降低Cu质量分数,2种合金的残余结晶相数量减少,力学性能提高,但Al-Zn-Mg-Cu-Zr合金抗腐蚀性能逐渐降低,Al-Zn-Mg-Cu-Zr-Cr-Yb合金抗腐蚀性能先升高后降低。在铜质量分数（0.8%Cu）较低时,与Al-Zn-Mg-Cu-Zr合金相比,复合添加Cr和Yb的合金,保持了超高强度性能,且抗腐蚀性能大幅度提高。

The effect of copper mass fraction（0.8%-2.2%） on microstructure and properties of Al-Zn-Mg-Cu-Zr alloy and Al-Zn-Mg-Cu-Zr-Cr-Yb alloy were comparatively studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, tensile test, intergranular corrosion, exfoliation corrosion and stress corrosion cracking test. The result shows that compared with the Al-Zn-Mg-Cu-Zr alloy, the composite additions of Cr and Yb on Al-Zn-Mg-Cu-Zr-Cr-Yb alloy can effectively inhibit the recrystallization and retard the grain growth, which can increase the strength and enhance the resistance to stress corrosion. With the decrease of the copper mass fraction, the volume fraction of residual eutectic phase decreases and the mechanical properties increase in the two kinds of alloys, while the corrosion resistance decreases in Al-Zn-Mg-Cu-Zr alloy, and first increases then decreases in Al-Zn-Mg-Cu-Zr-Cr-Yb alloy. Compared with Al-Zn-Mg-Cu-Zr alloy, the low copper mass fraction（0.8% Cu） Al-Zn-Mg-Cu-Zr-Cr-Yb alloy can keep the ultra-high strength performance and enhance the resistance to stress corrosion effectively.