Cu含量对T6及T8态时效超高强铝锂合金时效析出相和强度的不同影响

Different Effects of Cu Content on Aging Precipitation and Strength of T6-Aged and T8-Aged Ultra-High Strength Al-Li Alloys

摘要:

采用透射电子显微镜和室温拉伸性能测试，研究了Cu含量对Mg、Ag、Zn复合微合金化的新型超高强铝锂合金Al-xCu-1.2Li-X（x=4.2、4.5）冷轧薄板的时效析出相和强度的影响。结果表明：T6（165 ℃/24 h）及T8态时效时，不同Cu含量的超高强铝锂合金的析出相包括大量的T₁相、较多的θ′相、部分GP区和δ′/GP/δ′复合相以及少量的S′相；T6态时效时，高Cu含量更有利于合金中GP区及θ′相的析出而导致T₁相的数密度减少，因而强度较低、伸长率相对较高；T8时效时，高Cu含量则有利于T₁相和θ′相的同时析出，导致其数密度大幅度增加，同时S′相和GP区的析出受到抑制，因此随着Cu含量增加，合金强度增加、伸长率小幅度下降；T8态时效后，高Cu含量新型超高强铝锂合金的抗拉强度达661.7 MPa、伸长率约为6%。

Abstract:

Using transmission electron microscopy and tensile property tests， the effects of Cu content on the aging precipitates and strength of the ultra-high strength alloy Al-xCu-1.2Li-X（x=4.2， 4.5） cold-rolled sheets microalloyed with Mg， Ag， and Zn were studied. The results show that the strengthening precipitates of the T6-aged and T8-aged alloys include a large amount of T₁（Al₂CuLi） precipitates， a considerable amount of θ′（Al₂Cu） precipitates， part of GP zones and δ′/GP/δ′ composite phases， as well as a small amount of S′ precipitates. The higher Cu content in the T6-aged alloy facilitates the precipitation of GP zones and θ′ precipitates， whereas the number density of T₁ precipitates decreases， which results in the reduction of strength and slight increase of elongation. With the increase of Cu content in T8-aged alloy， the number density of T₁ and θ′ precipitates significantly increases， simultaneously inhibiting the nucleation of GP zones and S′ precipitates， contributing to an increase in the strength of T8-aged alloy with a slight decrease of elongation. The tensile strength of the T8-aged ultra-high strength Al-Li alloy with higher Cu content approaches to 661.7 MPa with the elongation of around 6%.