拉伸性能的影響
(1. 長沙學(xué)院 機電工程系，長沙 410003；
2. 中南大學(xué) 有色金屬材料科學(xué)與工程教育部重點實驗室，長沙 410083；
3. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用拉伸力學(xué)性能測試、透射電鏡微觀組織分析和掃描電鏡斷口分析等方法，研究熱暴露對一種欠時效態(tài)Al-Cu-Mg-Ag合金力學(xué)性能及微觀組織的影響。結(jié)果表明：在150 ℃熱暴露下，欠時效態(tài)Al-Cu-Mg-Ag合金的剩余強度先上升后下降，強度峰值出現(xiàn)在100 h；熱暴露1 000 h后，合金的力學(xué)性能相對欠時效態(tài)合金的無明顯下降；在200~300 ℃熱暴露時，合金強度隨時間的延長而下降，伸長率隨著時間的延長而增大；在300 ℃熱暴露時，強度明顯下降，熱暴露10 h后，其抗拉強度只有272.5 MPa，暴露100 h后, 其抗拉強度降至114.5 MPa；欠時效態(tài)合金細(xì)小分布的Ω相隨著熱暴露溫度的升高，Ω相長大并粗化，θ′相析出，無沉淀析出帶(PFZ)變寬；在250 ℃下熱暴露時，Ω相明顯粗化且數(shù)量稀少；合金中的Ω相和θ′相在300 ℃熱暴露100 h后，均轉(zhuǎn)變成平衡θ相。
關(guān)鍵字: Al-Cu-Mg-Ag合金；欠時效；熱暴露；力學(xué)性能；顯微組織
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
