一种新型超高强铝锂合金的力学性能与微观组织演化

Tensile Properties and Microstructure Evolution of a New Ultra-High Strength Al-Li Alloy

摘要:

铝锂合金作为一种轻质高强的结构材料，广泛应用于航空航天制造领域。为进一步提高铝锂合金强度，制备了一种含Cu为4.68%（质量分数）、Li为1.36%（质量分数）的Mg+Ag+Zn多元微合金化的新型超高强铝锂合金，并且系统地研究了该合金冷轧薄板（厚2 mm）的T6时效态（170 ℃）及T8时效态（4%预变形/150 ℃）的微观组织和力学性能。研究结果表明：该新型超高强铝锂合金，其T6时效态抗拉强度最高达637 MPa、T8时效态抗拉强度最高达685 MPa，强度达到峰值后伸长率随时效时间的继续延长从8%缓慢下降；该合金主要强化相为T1相（Al₂CuLi）和θ′相（Al₂Cu），T8时效态加速了T1相析出，从而加快了时效响应速度，同时增加了T1相数密度，提高了合金强度。说明，通过调整铝锂合金的时效状态可影响强化相总量及各析出相体积分数，从而获得更高强度的铝锂合金。

Abstract:

A new ultra-high strength Al-Li alloy containing 4.68 wt.% Cu and 1.36 wt.% Li and multi-microalloying elements of Mg+Ag+Zn was fabricated in this study. Tensile properties and microstructures of the Al-Li alloy cold rolled sheet with 2 mm thickness were investigated. The Al-Li alloy went through T6（170 ℃） and T8（4% pre-deformation/150 ℃） aging treatment before tensile testing and microstructure observations. The experimental results showed that the maximum ultimate tensile strengthes of the T8 and T6 aged alloy were around 685 MPa and 637 MPa， respectively. After peak aging， the elongation decreased slowly from 8% with further extension of the aging time. The main strengthening precipitates of the alloy were T1（Al₂CuLi） and θ′（Al₂Cu）. T8 aging treatment accelerated the precipitation of T1， which enhanced the aging response and increased the number density of T1 precipitates， and therefore improved the strength of the Al-Li alloy.