Abstract
The comprehensive performance of Al-Zn-Mg-Cu alloy can be significantly improved by a proposed novel thermo-mechanical treatment (NTMT). The influence of the NTMT on the properties and microstructure was investigated by tensile test, corrosion resistance test, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results show that Al-Zn-Mg-Cu alloy treated by the NTMT can obtain an excellent combination of strength and ductility. The highest yield strength and ultimate tensile strength reached 643 MPa and 664 MPa respectively, and the elongation was 9.7%. Meanwhile, electrochemical corrosion resistance and intergranular corrosion resistance in the aluminum alloy can be improved after the NTMT. The mechanism of the excellent combination of strength and ductility is thought to be the synergistic effect of dislocations substructures, texture configuration, and nanoprecipitates. The improvement of intergranular corrosion resistance of the aluminum alloy is caused by changes in the micro-morphology of grain boundary precipitates after the NTMT, which can block anodic dissolution channels along grain boundaries to reduce the rate of anodic dissolution and avoid hydrogen embrittlement.
Highlights
Al-Zn-Mg-Cu alloys can be used in aerospace and construction materials due to their high strength, low density, and good thermal processing performance, and they have a great application prospect [1,2,3,4]
We proposed the novel thermo-mechanical treatment (NTMT) based on continuous Solid solution-Hot rolling to solve the preparation of high strength and good ductility Al-Zn-Mg-Cu alloy with good intergranular corrosion resistance, which might provide a new idea for the preparation of high comprehensive properties aluminum alloys to meet the demand for aerospace and other high technology
An outstanding combination of strength and ductility is achieved in the condition of 30% continuous Solid solution-Hot rolling (SSHR) +60% cold rolling (CR) +ageing treatment (120°C/6 h), the highest yield strength (YS) and ultimate tensile strength (UTS) reached 643 MPa and 664 MPa respectively, the elongation was 9.7%
Summary
Al-Zn-Mg-Cu alloys can be used in aerospace and construction materials due to their high strength, low density, and good thermal processing performance, and they have a great application prospect [1,2,3,4] They are sensitive to intergranular corrosion (IGC), stress corrosion cracking (SCC), and exfoliation corrosion (EXCO) [5, 6], which limit their practical application. In 1974, the Israeli Cina [8] put forward a multi-step ageing process named the regression and re-ageing (RRA), in which the corrosion resistance of aluminum alloys was improved without sacrificing strength simultaneously. It is not convenient for large-scale applications since the alloy plate is required to be kept at a high temperature for a short retrogression time
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