Microstructural evolution and mechanical properties of ultrafine-grained pure α-iron and Fe-0.02%C steel processed by high-pressure torsion: Influence of second-phase particles

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:795

Article

Zhang, Yinyin¹  Sao-Joao, Sergio¹  Descartes, Sylvie²  Kermouche, Guillaume¹  Montheillet, Frank¹  Desrayaud, Christophe¹ 

[1] Univ Lyon, SMS Div, Ecole Mines St Etienne, CNRS,UMR 5307, F-42023 Lyon, France

[2] Univ Lyon, LaMCoS, INSA Lyon, CNRS,UMR 5259, F-69621 Lyon, France

关键词: High-pressure torsion;    Grain refinement;    Second-phase particles;    CDRX;    GDRX;   

DOI  :  10.1016/j.msea.2020.139915

来源: Elsevier

【 摘 要 】

A Fe-0.02 wt%C, containing cementite particles, and a pure a-iron are subjected to unconstrained high-pressure torsion and their microstructural refinement with strain are examined by electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction EBSD (TKD-EBSD), based on which the influence of second-phase particles on grain refinement mechanisms is investigated. Both materials are refined rapidly by formation of subgrain boundaries and grain boundaries at low and medium strains. The single-phase iron generates a higher density of geometrically necessary dislocations and forms small grains in the deformation inhomogeneity regions. However, at a higher strain of similar to 12.3, the cementite particles facilitate to overcome the saturation microstructure that occurrs in the pure iron and promote further grain refinement. Continuous dynamic recrystallization (CDRX) by transforming subgrain boundaries to grain boundaries is the major grain refinement mechanism before epsilon(vm)similar to 12-13. Geometric dynamic recrystallization (GDRX) is also operating during ultrahigh strains (epsilon(vm)similar to 12-30), particularly prevalent in the cementite-containing specimen. Mechanical properties of the HPT-processed microstructures are examined by nanoindentation and micropillar compression.

【 授权许可】

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