Prior Structure Modification on Grain Refinement and Deformation Behavior of Medium Carbon Steel Processed by ECAP. Issue 12 (20th June 2013)

• Record Type: Journal Article
• Authors: Zrnik, Jozef; Dobatkin, Sergey V.; Kraus, Libor; Raab, George
• Other Names: Tieu A. Kiet sponsoringEditor.; Zhu Hongtao sponsoringEditor.; Zhu Qiang sponsoringEditor.
• Is Part Of: Steel research international. Volume 84:Issue 12(2013:Dec.)
• Page Start: 1340
• Page End: 1346
• Publication Date: 2013-06-20
• Subjects: carbon steel -- microstructure -- TM treatment -- SPD -- ECAP -- properties; Steel -- Periodicals; Steel -- Metallurgy -- Periodicals; 669.142
• DOI: 10.1002/srin.201300118
• Languages: English
• ISSNs: 1611-3683

Abstract

Abstract : The present work, deals with grain refinement of medium carbon steel AISI 1045 (0.45% C), having different initial ferrite–pearlite microstructure resulted from thermal and thermomechanical treatment (TM). The purpose of TM steel processing was to refine ferrite and modify pearlite lamellae structure. The final grain refinement of steel structure was then accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. Employment of this processing route, in dependence of the applied effective strain ϵ ef, resulted in extensive deformation of ferrite grains and cementite lamellae fragmentation. When applying higher shear stress ( ϵ ef = 4) the mixed structure of subgrains and ultrafine grains was formed within ferrite phase, regardless the initial steel structure morphology. In pearlite grains, modification of cementite lamellae due to shearing, bending, twisting, and breaking was found efficient as straining increased. Processes of dynamic polygonization and recrystallization in deformed structure also contributed to submicrocrystalline grains formation in deformed structure. Comparing results the course of lamellae cementite spheroidization was then more efficient in prior TM treated steel. The tensile deformation results confirmed the strength increase, however deformation behavior and strain hardening generally for different initial structural conditions of steel, showed diversity. Abstract : In order to modify initial microstructure of medium carbon steel AISI 1045 the thermal and thermomechanical (TM) treatments are applied. The final grain refinement of both steel structural states is thereafter completed during ECAP severe plastic deformation (SPD) applying different strain ϵ ef . SPD processing resulted in extensive deformation of ferrite grains and cementite lamellae modification. Evaluating results, the course of grains refinement and lamellae modification is more effective in steel, which was preliminary modified by TM.