(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(diǎn)實(shí)驗(yàn)室，長沙 410083；
3. 中南大學(xué) 有色金屬先進(jìn)結(jié)構(gòu)材料與協(xié)同創(chuàng)新中心，長沙 410083；
4. 河南航天精工制造有限公司，信陽 464000)
摘 要: 通過電導(dǎo)率、力學(xué)性能測試和慢應(yīng)變速率拉伸試驗(yàn)，結(jié)合掃描電鏡(SEM)、電子背散射衍射(EBSD)等微觀組織表征方法，研究固溶處理對緊固件用Al-Zn-Mg-Cu合金擠壓棒材電導(dǎo)率、力學(xué)性能和應(yīng)力腐蝕性能的影響。結(jié)果表明：強(qiáng)化固溶較單級固溶處理，合金具有較好的電導(dǎo)率和力學(xué)性能。隨著強(qiáng)化固溶中二級固溶時(shí)間的延長和一級、二級固溶溫度的提高，電導(dǎo)率和伸長率隨之提高，硬度和強(qiáng)度隨之降低。其中，二級固溶時(shí)間的影響最大，其次是二級固溶溫度，一級固溶溫度的影響最小。隨著二級固溶時(shí)間的延長和溫度的提高，應(yīng)力腐蝕敏感指數(shù)(ISSRT)先減小后增大，主要因?yàn)闅堄啻执笙鄿p少，降低腐蝕敏感性，而后再結(jié)晶分?jǐn)?shù)提高和晶粒長大，惡化應(yīng)力腐蝕性能。在滿足緊固件用Al-Zn-Mg-Cu合金對電導(dǎo)率要求(≥38.0%IACS)的基礎(chǔ)上，獲得良好綜合性能適宜的熱處理工藝為：((450 ℃, 1 h)+(490 ℃, 1 h))固溶處理+ ((120 ℃, 5 h)+(177 ℃, 16 h))時(shí)效處理，合金的抗拉強(qiáng)度、硬度、電導(dǎo)率和應(yīng)力腐蝕敏感指數(shù)分別為532.8 MPa、158.0 HV、38.5%IACS和ISSRT為2.0%。
關(guān)鍵字: Al-Zn-Mg-Cu合金；組織；強(qiáng)化固溶；應(yīng)力腐蝕性能
（1. School of Material 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;
3. Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China;
4. Henan Aerospace Precision Machining Co., Ltd., Xinyang 464000, China）
Abstract:The effects of solution treatment on conductivity, mechanical properties and stress corrosion resistance of the Al-Zn-Mg-Cu alloy extruded bars for fasteners were investigated by electrical conductivity, mechanical properties and slow strain rate tensile tests, combined with scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD). The results show that the alloys treated by enhanced solution have better conductivity and mechanical properties than single-stage solution treated alloys. The conductivity and elongation increase and the hardness and strength decrease with the extending of secondary solution time and the increasing of primary and secondary solution temperature. While the second solution time has the most influential on conductivity and mechanical properties of alloys, which is followed by second solution temperature, and first solution temperature has the least effect. The stress corrosion sensitivity index (ISSRT) decreases and then increases with the extending of the second solution time and the increasing of temperature. The decrease of residual coarse phase is the mainly responsible for the decreasing of corrosion sensitivity. And then, the crystallization fraction increases and the grain grows, which worsens the stress corrosion performance. On the basis of meeting the requirements of the conductivity(≥38.0%IACS) of Al-Zn-Mg-Cu alloy used for fasteners, the suitable heat treatment process for good comprehensive properties are ((450 ℃, 1 h)+(490 ℃, 1 h)) solution treatment+((120 ℃, 5 h)+(177 ℃, 16 h)) aging treatment. The tensile strength, hardness and conductivity of the alloy are 532.8 MPa, 158.0HV and 38.5%IACS, respectively, ISSRT is 2.0%.
Key words: Al-Zn-Mg-Cu alloy; structure; enhanced solid solution; stress corrosion resistance
