(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 东北轻合金有限责任公司，哈尔滨 150060)
摘 要: 采用力学性能测试和电子显微分析技术研究了不同加工处理条件下Al-5.4Zn-2.0-Mg-0.25Cu-0.1Sc-0.1Zr合金的显微组织及性能演变。结果表明：在半连续激冷铸造条件下，铸锭存在晶界偏析，形成了富Zn、Mg的非平衡相和富Fe、Si、Mn的杂质相；经470 ℃、12 h均匀化处理后，富Zn、Mg的非平衡相溶入基体，仅剩下少量富Fe、Si、Mn的杂质相；与此同时，铸锭合金固溶体分解析出纳米级的Al3(Sc, Zr)相，470 ℃、12 h是研究合金合适的铸锭均匀化制度；铸锭热变形过程中，随试验温度升高合金强度逐渐降低，伸长率则先增加而后降低，350~400 ℃的温度范围内合金具有较稳定的热变形抗力和塑性，是合宜的热变形温度范围；合金冷轧板材经 470 ℃、1 h固溶处理后，热变形过程中形成的大量非平衡相溶入基体形成过饱和固溶体，时效过程中脱溶顺序为αsss(α过饱和固溶体)®GP区®η′相®η相。合金板材最佳固溶−时效工艺为（470 ℃, 1 h）固溶+(120 ℃, 24 h)时效，在此条件下，试验合金的抗拉强度、屈服强度和伸长率分别可达533 MPa、494 MPa和15%。试验合金的高强度主要来源于η′相析出强化、添加微量Sc和Zr引起的亚晶强化和亚结构强化以及Al3(Sc, Zr)相的弥散强化。
关键字: Al-Zn-Mg-Sc-Zr合金；板材；铸锭均匀化；热塑性；固溶−时效；组织；力学性能；演变
its microstructure-properties evolution
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Northeast Light Alloy Co., Ltd., Harbin 150060, China）
Abstract:The evolution of microstructure and properties of Al-5.4Zn-2.0Mg-0.25Cu-0.1Sc-0.1Zr under different processing and heat treatment conditions was studied using mechanical properties measurement and electron microscopy. The results show that, under semi-continuous casting conditions, at grain boundaries there is some segregation which is bearing Zn, Mg non-equilibrium phases and indissoluble impurity phases containing Fe, Si and Mn elements. After the homogenization at 470 ℃ for 12 h the non-equilibrium phases dissolve into matrix completely and only small amounts of indissoluble phases still exist. At the same time, the solid solution matrix precipitates nano-scaled Al3(Sc, Zr) dispersoid particles. The proper homogenization treatment processing of the ingot is at 470 ℃ for 12 h. During the hot deformation of ingot, with the increase of deformation temperatures, the strength decreases, the elongation increases firstly and then decreases. Between 350 ℃ and 400 ℃ the alloy is of a more stable deformation characteristics and this is the suitable deformation temperature range for this alloy. After solutioning at 470 ℃ for 1 h lots of non-equilibrium phases formed during hot rolling dissolve into the matrix. The precipitation sequence of the alloy during aging is described
as follows: supersaturated solid solution (α)→GP zones→metastable η′ phase→η phase. The suitable solution-aging treatment processing of the studied alloy is solution-treated at 470 ℃ for 1 h, followed by water quenching and then aged at 120 ℃ for 24 h. Under this condition, the ultimate tensile strength, yield strength and elongation of the studied alloy plate could reach 533 MPa, 494 MPa and 15%, respectively. The strengthening mechanism of the studied alloy is precipitation strengthening of fine η′ phase, subgrain strengthening and dispersion strengthening caused by Al3(Sc, Zr) dispersoid particles.
Key words: Al-Zn-Mg-Sc-Zr alloy; plate; ingot homogenization; thermal plasticity; solution-aging; microstructure; mechanical properties; evolution
