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Vol.51, No.5, 333 ~ 341, 2013
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| Title |
| Effects of Cryogenic Treatment on Residual Stress and Precipitation for 7075 Aluminum Alloy |
| 김회봉 Hoi Bong Kim , 김동용 Dong Yong Kim , 고대훈 Dae Hoon Ko , 김병민 Byung Min Kim , 조영래 Young Rae Cho |
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| Abstract |
| To develop 7075 aluminum (Al7075) alloy with low residual stress and high strength, a modified cryogenic treatment was proposed. In this study, the effects of two additional steps on residual stress in Al7075 were investigated. Unlike the conventional age-hardening process, the first step of the modified treatment is cryogenic quenching, followed by the second step of uphill quenching of the samples. The mechanical properties and residual stress of samples were characterized by Vickers hardness and X-ray diffraction with sin2 method, respectively. Structural properties such as size and formation of the precipitates of the samples were characterized by transmission electron microscopy and electron energy loss spectroscopy. Three different uphill quenching methods, boiling water, room temperature water, and air, were applied to the samples. Samples treated by the boiling water uphill quenching method showed the lowest residual stress and highest hardness. Results clearly demonstrated that the modified cryogenic treatment with boiling water uphill quenching method was a very useful heat treatment to achieve an age-hardened Al7075 alloy with low distortion shape, low residual stress and high hardness. |
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| Key Words |
| alloys, aging, residual stress, transmission electron microscope, cryogenic treatment |
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