(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083；
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)
摘 要: 通過末端淬火實驗(JEQ)、X射線衍射儀(XRD)、掃描電鏡(SEM)、透射電子顯微鏡(TEM)研究一種熱擠壓Al-Zn-Mg-Cu-Sc-Zr棒材的淬火敏感性。結(jié)果表明：隨著距離淬火端越遠，冷卻速率從1800 ℃/min下降至111 ℃/min，合金硬度從150 HB下降至133 HB，抗拉強度從430 MPa下降至375 MPa。當(dāng)冷卻速率為131.2 ℃/min時，合金的硬度為135 HB，合金淬透深度約為93mm。隨著冷卻速率的降低，端淬時遠離淬火端位置，平衡η相先后在晶界、晶內(nèi)處析出、長大、粗化；時效后，析出的η′強化相的數(shù)量減小；時效后，合金內(nèi)出現(xiàn)無沉淀析出帶(PFZ)，晶界的PFZ變寬，寬化至160 nm。
關(guān)鍵字: Al-Zn-Mg-Cu-Sc-Zr合金；淬火敏感性；力學(xué)性能；顯微組織
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China）
Abstract:The quench sensitivity of the Al-7.01Zn-1.39Mg-2.25Cu-0.07Zr-0.07Sc alloy were investigated by the Jominy end-quench(JEQ) test, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that, with the increase of the distance from the quenched end of the bar (d) and the decrease of average cooling rates from 1800 ℃/min to 111 ℃/min, the hardness falls to 133 HB from 150 HB and the tensile strength falls to 375 MPa from 430 MPa. When the critical average cooling rate is about 131.2 ℃/min and the d is 93 mm, 90% of the maximum hardness can be obtained. As the cooling rate reduces, the microstructure change as follows: the η equilibrium phase forms in the grain boundary and grained at different positions from the quenching end in the JEQ process in sequence, the number of η′ strengthening precipitates decreases after aging, the width of precipitate free zone near grain boundaries reaches up to 160 nm.
Key words: Al-Zn-Mg-Cu-Sc-Zr alloy; quench sensitivity; mechanical properties; microstructures
