Microstructure of stir zone in friction stir welded joint of Al-Zn-Mg-Cu aluminum alloy thick plate

doi:10.13251/j.issn.0254-6051.2022.01.023

Abstract

Abstract: By using FSW (friction stir welding) technology, a 20 mm thick Al-Zn-Mg-Cu aluminum alloy plate was welded, and then the temperature distribution of the welded joints and the microstructure inhomogeneity in the stir zone along thickness direction were studied by using thermocouple, electron backscatter diffraction technology and transmission electron microscope. The results show that the peak welding temperature gradually decreases along the thickness direction. At 10 mm from the center of weld, the welding peak temperature on the surface of plate is maximum of 430 ℃, and that on the bottom surface of the plate is minimum of 302 ℃. The temperature gradient is the main reason that the grain size gradually decreases along the thickness direction. The grain refinement is the result of the combined effects of continuous dynamic recrystallization, discontinuous dynamic recrystallization and geometric dynamic recrystallization. There is no obvious preferred orientation of grains in the stir zone, and the precipitates in this zone are dissolved and then precipitated, and the precipitates are mainly η′ phase.

Key words: friction stir welding, temperature field, dynamic recrystallization, precipitate, grain size

CLC Number:

TG401

Qiang Fei, Wang Wen, Zhang Ting, Yang Juan, Cai Jun, Wang Kuaishe. Microstructure of stir zone in friction stir welded joint of Al-Zn-Mg-Cu aluminum alloy thick plate[J]. Heat Treatment of Metals, 2022, 47(1): 135-141.

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