Effect of Non-Isothermal Ageing on Microstructure and Properties of 7B50 Aluminum Alloy
Received date: 2020-01-02
Revised date: 2020-04-08
Online published: 2020-04-16
Supported by
National Natural Science Foundation of China(51801082);Natural Science Foundation of Jiangsu Province(BK20160560);Undergraduate Innovation and Entrepreneurship Training Program of Jiangsu Province(201910289095Y)
Due to the temperature rising or cooling stage in thick plate, non-isothermal ageing has been the research hotspot of heat treatment for Al-Zn-Mg-Cu alloy thick plate. It is possible to replace the isothermal ageing by non-isothermal one because of the high efficiency and practicability. As one of the Al-Zn-Mg-Cu alloy, 7B50 aluminum alloy and its thick plate have supposed to manufacture the wing in "Yun-20" big plane. In this work, hardness test, electrical conductivity test, room temperature tensile test, DSC analysis, exfoliation corrosion test and TEM observation were used to study the influence of non-isothermal ageing on microstructure and corrosion resistance of 7B50 aluminum alloy hot rolling thick plate. Results revealed that, after 480 ℃, 1 h solution and quenched in room temperature water, followed by ageing from room temperature to 215 ℃ at 1 ℃/min heating rate, and furnace cooling to room temperature immediately, the inner precipitates of 7B50 aluminum alloy are fine and dispersed while the ones on grain boundary are coarsened and discontinuous. The tensile strength and exfoliation corrosion grade reached to 605 MPa and EB level, respectively. Comprehensive performance of 7B50 aluminum alloy are excellent overall those of isothermal peak ageing (T6) or isothermal double stages over ageing (T76), but similar to that of retrogression and re-ageing (RRA) treatment. The non-isothermal ageing realized the short process preparation and the measure removing isothermal stage is more suitable for thick plates.
Jichen LI , Di FENG , Weisheng XIA , Gaoyong LIN , Xinming ZHANG , Minwen REN . Effect of Non-Isothermal Ageing on Microstructure and Properties of 7B50 Aluminum Alloy[J]. Acta Metall Sin, 2020 , 56(9) : 1255 -1264 . DOI: 10.11900/0412.1961.2020.00004
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