淬火方式对7050铝合金挤压棒材组织和性能的影响研究

Effect of Quenching Method on Microstructure and Properties of 7050 Aluminium Alloy Extruded Bar

以ϕ75 mm7050铝合金棒材为研究对象,分别采用离线和在线方式对试样进行淬火处理,然后进行时效处理。采用OM、SEM、EDS、TEM和电子拉伸试验机分析测试了在线及离线淬火试样的组织和拉伸性能,并对结果进行了比较;对离线及在线淬火试样进行应力腐蚀试验及剥落腐蚀试验,比较了两种淬火方式下试样的耐腐蚀性能。结果表明:在线淬火试样基体中的第二相数量远多于离线淬火试样。离线淬火试样晶内析出相以杆状η′相为主,还存在部分η相。在线淬火试样晶内可见大量纠缠聚集的GP区,存在部分η′相和少量η相。在线淬火试样由于固溶温度低、淬火冷速不足,降低了过饱和固溶体的溶质浓度,进而减少了时效沉淀强化相的数量,导致在线淬火试样的强度降低。在线与离线淬火试样的电导率、应力腐蚀性能和剥落腐蚀性能均符合相关标准要求。双级时效能有效改善铝合金抗应力腐蚀性能及耐剥落腐蚀性能,抗腐蚀性能较峰值时效也具有一定优势。

Takingϕ75 mm 7050 aluminium alloy bar as the research object,the samples were quenched offline and online respective⁃ly,and then aged.The microstructure and tensile properties of the offline and online quenched samples were analyzed and tested by OM,SEM,EDS,TEM and electronic tensile testing machine,and the results were compared.Stress corrosion test and exfoliation cor⁃rosion test were carried out on the two samples,and the corrosion resistance of the samples under the offline and online quenched quenching methods was compared.The results show that the amount of the second phase in the matrix of the online quenched sample is much more than that of the offline quenched sample.The precipitated phase in the offline quenched sample of 7050 aluminium al⁃loy bar after ageing is mainly rod-likeη'phase,and there are someηphases.A large number of entangled GP regions can be seen in the grains of online quenched samples,with someη'phase and a small amount ofηphase.Due to the low solution temperature and insufficient quenching cooling rate,the solute concentration of susaturated solid solution is reduced,and the amount of ageing precipi⁃tation strengthening phase is reduced,resulting that the strength of online quenched sample is reduced.The electrical conductivity,stress corrosion properties and exfoliation corrosion properties of the online and offline quenched samples meet the requirements of rel⁃evant standards.The two step stage ageing can effectively improve the stress corrosion resistance and exfoliation corrosion resistance of aluminium alloy,and the corrosion resistance has certain advantages over the peak ageing.