Influence of Retrogression Time on Mechanical Properties and Microstructure of 7150 Aluminum Alloy
Yan ZHANG1, Yun-lai DENG1,2,*(), Shi-tong FAN2, Tao LONG2
1 Light Alloy Research Institute, Central South University, Changsha 410083, China 2 School of Materials Science and Engineering, Central South University, Changsha 410083, China
The influence of the retrogression time on properties and microstructure of 7150-T77 aluminum alloy was studied by hardness testing, tensile property testing, exfoliation corrosion test and TEM. Results indicate that the matrix precipitated η' phase re-dissolves first, and then η phase re-precipitates and becomes coarsened with the extending of retrogression time. The ultimate mechanical properties increase first then decrease as retrogression time increases. The critical time of the η' phase re-dissolution and the η phase precipitation is 30min, At this point, alloys have the highest ultimate mechanical properties, and the grain boundary precipitated η phase becomes coarsened and discontinuous, leading to lower mechanical properties and better corrosion resistance, peak hardness exists at re-aging stage. With the retrogression time extending, the time for the alloy to reach the peak hardness becomes shorter. Optimal T77 aging treatment is 105℃/17h+190℃/30min+120℃/23h. With this treatment, the ultimate tensile strength (σb), yield strength (σ0.2) and elongation (δ) are 608, 544MPa and 10.4%, respectively, the exfoliation corrosion test gets EA level, the σb and δ loss in constant loading tensile testing is 4.9% and 5.0%, respectively.
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Yan ZHANG, Yun-lai DENG, Shi-tong FAN, Tao LONG. Influence of Retrogression Time on Mechanical Properties and Microstructure of 7150 Aluminum Alloy. Journal of Materials Engineering, 2018, 46(12): 131-136.
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