拉伸性能的影响
(1. 长沙学院 机电工程系,长沙 410003;
2. 中南大学 有色金属材料科学与工程教育部重点实验室,长沙 410083;
3. 中南大学 材料科学与工程学院,长沙 410083)
摘 要: 采用拉伸力学性能测试、透射电镜微观组织分析和扫描电镜断口分析等方法,研究热暴露对一种欠时效态Al-Cu-Mg-Ag合金力学性能及微观组织的影响。结果表明:在150 ℃热暴露下,欠时效态Al-Cu-Mg-Ag合金的剩余强度先上升后下降,强度峰值出现在100 h;热暴露1 000 h后,合金的力学性能相对欠时效态合金的无明显下降;在200~300 ℃热暴露时,合金强度随时间的延长而下降,伸长率随着时间的延长而增大;在300 ℃热暴露时,强度明显下降,热暴露10 h后,其抗拉强度只有272.5 MPa,暴露100 h后, 其抗拉强度降至114.5 MPa;欠时效态合金细小分布的Ω相随着热暴露温度的升高,Ω相长大并粗化,θ′相析出,无沉淀析出带(PFZ)变宽;在250 ℃下热暴露时,Ω相明显粗化且数量稀少;合金中的Ω相和θ′相在300 ℃热暴露100 h后,均转变成平衡θ相。
关键字: Al-Cu-Mg-Ag合金;欠时效;热暴露;力学性能;显微组织
underaged Al-Cu-Mg-Ag alloy
(1. Department of Mechanical and Electronic Engineering, Changsha University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China;
3. School of Materials Science and Engineering, Central South University, Changsha 410083, China)
Abstract: The effects of long term thermal exposure on mechanical properties and microstructures of an underaged Al-Cu-Mg-Ag alloy were investigated by tensile test, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that the residual strength of underaged samples appears to increase first whereas then decrease, the peaking strength is obtained after exposuring at 150 ℃ for 100 h. Compared with the underage condition, the mechanical properties of the underaged Al-Cu-Mg-Al alloys have no obvious variation after exposuring for 1 000 h, which represent superior heat resistance. The residual strengths of underage samples decrease versus elongation increases as the exposure time prolongs and temperature rises from 200 to 300 ℃. The tensile strengths of the samples are 272.5 MPa and 114.5 MPa after exposuring at 300 ℃ for 10 h and 100 h, respectively, revealing obvious reduce in strength. With increasing exposure temperature and/or time, the thickening kinetics of Ω phase greatly increases and the precipitation free zones are broadened at grain boundary. Finally, Ω and θ′ phases are replaced by equilibrium θ phase, which decreases the strength of the alloy.
Key words: Al-Cu-Mg-Ag alloy; underage; thermal exposure; mechanical properties; microstructure