High-temperature retrogression and re-aging process of Al-6.8Zn-2.3Mg-2.0Cu-0.15Sc alloy

doi:10.13251/j.issn.0254-6051.2020.07.013

Abstract

Abstract: Properties and microstructure evolution laws of Al-6.8Zn-2.3Mg-2.0Cu-0.15Sc alloy in the process of high-temperature retrogression and re-aging (RRA) were studied via technological means such as sclerometer, digital eddy current metal conductometer, transmission electron microscope (TEM), universal tensile testing machine and scanning electron microscope (SEM). The results show that in the retrogressive process at 170 ℃ the alloy has high hardness and excellent electrochemical corrosion resistance. The principal phase η′ of the alloy is fine, dispersed and numerous after the retrogressive process at 170 ℃ for 1 h, and it strengthens the alloy with Orowan mechanism by virtue of dislocation cutting in the process of deformation. Therefore, it achieves the strength of 625.1 MPa and the elongation of 9.6 %, and is superior to one-step aging (T6) G.P. area with the strength of 592.4 MPa and the elongation of 6.5%. The strength is enhanced by 32.7 MPa and the elongation is increased by 47.7%. In addition, the appearance of tensile fracture presentes a complete ductile fracture characteristic via SEM. The excellent RRA process of the Al-6.8Zn-2.3Mg-2.0Cu-0.15 Sc alloy is aging at 140 ℃ for 24 h, regression aging at 170 ℃ for 1 h and re-aging at 160 ℃ for 24 h.

Key words: high-temperature retrogression and re-aging, electrical conductivity, strengthening mechanism

CLC Number:

TG146.21

Shi Wenjie, Wang Chunhua. High-temperature retrogression and re-aging process of Al-6.8Zn-2.3Mg-2.0Cu-0.15Sc alloy[J]. Heat Treatment of Metals, 2020, 45(7): 63-67.

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