Influence of pre-aging time on microstructure and properties  of 7A85 aluminum alloy during RRA process

doi:10.13251/j.issn.0254-6051.2022.03.008

Abstract

Abstract: Influence of pre-aging time on microstructure and properties of the 7A85 aluminum alloy during RRA process was investigated. The thermodynamic equilibrium phase transformation and TTT curves were calculated by Jmat-Pro. The hardness and tensile properties were tested and microstructure was characterized by means of TEM. The results indicate that MgZn₂ phase begins to precipitate at 410 ℃ under thermodynamic equilibrium, volume fraction of which reaches about 9.5%. The GP zone is precipitated first during the isothermal process in the temperature range of room temperature to 175 ℃, and the nose tip temperature is about 150 ℃. With the extension of pre-aging time, the hardness first increases and then decreases, and reaches a peak hardness of 192 HV after aging for 20 h. The yield strength and tensile strength reach the peak value of 625 MPa and 675 MPa, respectively, when the pre-aging time is 20 h during the RRA process. During the heat preservation process at 120 ℃, under the peak aging state of 20 h, the size of the η′-MgZn precipitated phase is 5-10 nm. When the pre-aging time is 12 h, the Al-Zn-Mg-Cu quaternary phase particles with the size of 50-125 nm at the grain boundaries are discontinuously distributed after RRA treatment.

Key words: 7A85 aluminum alloy, pre-aging treatment, RRA treatment, microstructure, hardness

CLC Number:

TG156.1

Yang Chunmiao, Wang Shan, Wang Shuhui, Li Yanzhen, Liu Wenwen. Influence of pre-aging time on microstructure and properties of 7A85 aluminum alloy during RRA process[J]. Heat Treatment of Metals, 2022, 47(3): 44-47.

References

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Influence of pre-aging time on microstructure and properties of 7A85 aluminum alloy during RRA process

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