Effect of annealing process on microstructure and microhardness of magnesium alloy fabricated by friction stir processing

doi:10.13251/j.issn.0254-6051.2020.05.027

Abstract

Abstract: Friction stir processing (FSP) technology was adopted to prepare AZ31 magnesium alloy. The microstructure evolution and microhardness of the FSP magnesium alloy during annealing was studied by varying annealing temperature and preserving time. The results show that the fine grained AZ31 magnesium alloy are successfully prepared by FSP, and the average grain size is refined by 54.9%. When the annealing temperature is between 200-300 ℃, the average grain size in the stirring zone (SZ) is rather stable, and the structure is homogenized and refined in different degrees. When the annealing temperature is higher than 300 ℃, in the SZ the grains grow rapidly by consuming each other. In the heat affected zone (HAZ), when the annealing temperature is low, the microstructural evolution is insignificant after short-time preservation, while long time preserving and high temperature makes the microstructure in the HAZ to be refined and homogenized rapidly. When the annealing temperature exceeds 300 ℃, the recrystallization will be completed in a short time, then the grains in the HAZ begin to grow again. Annealing at 300 ℃ for 60 min is the optimum annealing process, after which the microstructure in the SZ and the HAZ can be refined by 10.9% and 35.6%, respectively.

Key words: AZ31 magnesium alloy, friction stir processing, annealing process, microstructure, hardness

CLC Number:

TG146.2

Li Tianqi, Yin Chen, Yan Yuanyuan, Zhang Kuo, Wang Xi. Effect of annealing process on microstructure and microhardness of magnesium alloy fabricated by friction stir processing[J]. Heat Treatment of Metals, 2020, 45(5): 141-146.

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