Effect of high-temperature tempering on microstructure evolution and recrystallization mechanism of P91 steel

doi:10.13251/j.issn.0254-6051.2023.11.006

Abstract

Abstract: Phase transformation point of P91 steel was determined by thermal expansion method. The microstructure and the evolution of special grain boundaries of the P91 steel during tempering at 710, 730, 760, 770, 790, 810, 830 and 840 ℃ were studied by means of OM, TEM and EBSD. It is found that with the increase of tempering temperature, the lath martensite morphology in the P91 steel is weakened, the dislocation density is gradually reduced, and the equiaxed ferrite structure appears. By EBSD analysis, the content of high angle grain boundaries increases gradually with the increase of tempering temperature and tends to be stable, while the content of low angle grain boundaries is significantly reduced. The analysis shows that during the tempering process, recrystallization occurs and a certain amount of equiaxed ferrite is formed, which nucleates through the mechanism of subgrain polymerization migration and grain boundary expansion, so as to realize recrystallization.

Key words: P91 heat-resistant steel, tempering, recrystallization, microstructure evolution

CLC Number:

TG162.84

Zhou Hao, Wang Yun, Zeng Yanping. Effect of high-temperature tempering on microstructure evolution and recrystallization mechanism of P91 steel[J]. Heat Treatment of Metals, 2023, 48(11): 38-44.

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