Enhancement of mechanical properties by changing microstructure in the eutectoid steel

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 558; pp. 158 - 161
• Main Authors: Zheng, Chengsi, Li, Longfei, Yang, Wangyue, Sun, Zuqing
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.12.2012; Elsevier
• Subjects: Annealing; Applied sciences; Condensed matter: structure, mechanical and thermal properties; Duplex stainless steels; Dynamic transformation; Elasticity, elastic constants; Elasticity. Plasticity; Elongation; Eutectoid steel; Exact sciences and technology; Ferrite; Heat treatment; Lamellar structure; Mechanical and acoustical properties of condensed matter; Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metals. Metallurgy; Microstructure; Pearlite; Physics; Production techniques; Structural steels; Tensile strength; Work-hardening rate; Mechanical properties; Eutectoid steel; Work-hardening rate; Microstructure; Dynamic transformation; Hot deformation; Grain size; Scanning electron microscopy; Annealing; Work hardening; Eutectoid; Supercooled liquid; Plastic deformation; Tension test; Tensile strength; Lamellar structure; Yield strength; Supercooling; Elongation (mechanics)
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2012.07.105

The different microstructures of eutectoid steel were analyzed with SEM and its corresponding room-temperature tensile tests were carried out. The results show that the ultrafine (α+θ) duplex structure consisting of ferrite matrix (α) with grain size of about 1μm and dual-size distributed cementite particles (θ) could be formed by hot deformation of undercooled austenite and subsequent annealing. Moreover, the mixed microstructures consisting of polygonal ferrite grains with size of about 2μm and fine pearlite colonies could be also obtained by this process under different conditions. Although the yield strength and total elongation of ultrafine (α+θ) duplex structure increase markedly, its tensile strength decrease obviously comparing to that of lamellar pearlite. The lower work-hardening rate at the beginning of uniform plastic deformation is probably responsible for tensile strength decrease in the ultrafine (α+θ) duplex structure. Moreover, the tensile strengths and total elongations of mixed microstructures are both larger than that of ultrafine (α+θ) duplex structure and lamellar pearlite due to their well work-hardening capabilities.