Microstructure Evolution of a New Dual-Phase Steel via Multi-Pass Compression Deformation in the (α + γ) Region

• Published in: Steel research international Vol. 87; no. 2; pp. 157 - 164
• Main Authors: Zhang, Chunling, Kong, Yuting, Zhang, Mengmeng, Yang, Jinfeng, Cai, Dayong
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.02.2016; Wiley Subscription Services, Inc
• Subjects: (α + γ) region; Carbon steel; Deformation; Microstructure; microstructure evolution; multi-pass deformation; Recrystallization; ultrafine ferrite grains
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.201400526

Grain refinement provides an effective way to improve the strength of low‐carbon steel without loss of room temperature ductility. The microstructure evolution of Cu–P–Cr–Ni–Mo weathering steel during multi‐pass deformation was investigated via hot compression simulation. The results indicated that ultrafine ferrite grains of 1.8 μm can be obtained in the (α + γ) region at multi‐pass deformation conditions. The second phase of bainite and martensite was distributed as band form on the ferrite matrix and became thinner with increasing number of passes. The microstructural analysis results showed that at the initial pass deformation, strain‐enhanced ferrite transformation is the main mechanism for structure refinement and at the later pass deformation, continuously dynamic recrystallization of ferrite is the main mechanism for ferrite grain refinement. Ferrite grain refinement is prominent at the initial pass deformation, and the average grain size reachs 1.8 μm after the fifth pass deformation. The LAGBs continuously transforms into HAGBs with increasing strain, and their misorientation increases gradually, thus causes the occurrence of grain refinement. The main refinement mechanism is the DRX of ferrite at the later pass deformation.