【摘要】 通过力学性能、电导率及拉伸应力腐蚀性能测试、扫描电镜及透射电镜观察,研究回归再时效(RRA)热处理工艺对一种新型低频电磁铸造合金Al-9.99%Zn-1.72%Cu-2.5%Mg-0.13%Zr(质量分数)的力学性能和抗应力腐蚀性能的影响,探讨RRA处理后合金的电导率与抗应力腐蚀性能的关系。研究结果表明:在峰值时效T6状态下合金强度高,但抗应力腐蚀性能差;采用合适的RRA热处理工艺既能使合金保持T6状态下的高强度的同时,又能显著改善合金的抗应力腐蚀性能;经回归7 min RRA处理后合金的晶界类似T73态析出相聚集粗化,而晶内类似T6态析出相细小弥散分布,在拉伸应力为210 MPa和3.0%NaCl+0.5%H2O2腐蚀液中,其断裂时间大于720 h,相应的抗拉强度、屈服强度和延伸率分别为795 MPa,767 MPa和9.1%,显示优越的综合性能。此外,RRA处理后合金的电导率与拉伸应力腐蚀性能为正相关。更多还原

【Abstract】 The effects of retrogression reaging（RRA） heat treatment on the mechanical properties and stress corrosion cracking（SCC） resistance,and the relationship between conductivity and SCC resistance of a low frequency electromagnetic casting alloy,Al-9.99%Zn-1.72%Cu-（2.5%Mg-0.13%Zr）（mass fraction）,were investigated by using the tensile testing and SCC resistance testing,Vickers hardness,electrical conductivity testing,scanning electron microscope（SEM） and transmission electron microscope（TEM）.The results show that proper RRA heat treatment can improve SCC properties with retention of the high strength of T6 level.After pre-aging at 100 ℃ for 24 h,retrogression at 200 ℃ for 7 min,and reaging at 100 ℃ for 24 h,the ultimate tensile strength,yield strength and elongation of the alloy are 795 MPa,767 MPa and（9.1%,） respectively.Meanwhile the failure time of the alloy applied to tensile strength of 210 MPa in（3.0%NaCl+）0.5%H₂O₂（corrosion） condition is longer than 720 h.The corresponding TEM observation shows that after retrogression for 7 min and re-aging treatment,the microstructure of grain boundary is similar to that treated in the T73 condition with coarsen and isolated distribution,and the microstructure inside grain is similar to that treated in the T6 condition with small and homogeneous distribution.Moreover,there exists a positive correlation between electric conductivity and SCC resistance of the alloy after RRA treatment.更多还原