TY - JOUR

T1 - Equal-channel angular sheet extrusion of interstitial-free (IF) steel

T2 - Microstructural evolution and mechanical properties

AU - Saray, O.

AU - Purcek, G.

AU - Karaman, I.

AU - Neindorf, T.

AU - Maier, H. J.

N1 - Funding information: This study was mainly supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under grant no. 107M618 and under 2219-International Postdoctoral Research Scholar Program. This study was also partly supported by Scientific Research Projects of Karadeniz Technical University , under grant no. 2008.112.003.6 . I. Karaman would like to acknowledge the supports from the US National Science Foundation , Division of CMMI, grant no. 0900187 and the US National Science Foundation, International Materials Institutes Program through the grant no. DMR 08-44082 , Office of Specific Programs, Division of Materials Research, Arlington, VA, USA. The authors would also like to thank Eregli Iron and Steel Company (ERDEMIR), Inc., Zonguldak, Turkey for their support in kindly supplying the initial materials.

PY - 2011/5/19

Y1 - 2011/5/19

N2 - Interstitial-free steel (IF-steel) sheets were processed at room temperature using a continuous severe plastic deformation (SPD) technique called equal-channel angular sheet extrusion (ECASE). After processing, the microstructural evolution and mechanical properties have been systematically investigated. To be able to directly compare the results with those from the same material processed using discontinuous equal channel angular extrusion, the sheets were ECASE processed up to eight passes. The microstructural investigations revealed that the processed sheets exhibited a dislocation cell and/or subgrain structures with mostly low angle grain boundaries. The grains after processing have relatively high dislocation density and intense micro-shear band formation. The electron backscattering diffraction (EBSD) examination showed that the processed microstructure is not fully homogeneous along the sheet thickness due probably to the corner angle of 120° in the ECASE die. It was also observed that the strengths of the processed sheets increase with the number of ECASE passes, and after eight passes following route-A and route-C, the yield strengths reach 463. MPa and 459. MPa, respectively, which is almost 2.5 times higher than that of the initial material. However, the tensile ductility considerably dropped after the ECASE. The limited ductility was attributed to the early plastic instability in the tensile samples due to the inhomogeneous microstructure. The specimen orientation with respect to the ECASE direction did not have a considerable effect on the stress-strain response. Appropriate low temperature annealing of ECASE-processed IF-steel resulted in a good strength-ductility balance.

AB - Interstitial-free steel (IF-steel) sheets were processed at room temperature using a continuous severe plastic deformation (SPD) technique called equal-channel angular sheet extrusion (ECASE). After processing, the microstructural evolution and mechanical properties have been systematically investigated. To be able to directly compare the results with those from the same material processed using discontinuous equal channel angular extrusion, the sheets were ECASE processed up to eight passes. The microstructural investigations revealed that the processed sheets exhibited a dislocation cell and/or subgrain structures with mostly low angle grain boundaries. The grains after processing have relatively high dislocation density and intense micro-shear band formation. The electron backscattering diffraction (EBSD) examination showed that the processed microstructure is not fully homogeneous along the sheet thickness due probably to the corner angle of 120° in the ECASE die. It was also observed that the strengths of the processed sheets increase with the number of ECASE passes, and after eight passes following route-A and route-C, the yield strengths reach 463. MPa and 459. MPa, respectively, which is almost 2.5 times higher than that of the initial material. However, the tensile ductility considerably dropped after the ECASE. The limited ductility was attributed to the early plastic instability in the tensile samples due to the inhomogeneous microstructure. The specimen orientation with respect to the ECASE direction did not have a considerable effect on the stress-strain response. Appropriate low temperature annealing of ECASE-processed IF-steel resulted in a good strength-ductility balance.

KW - Equal-channel angular extrusion/pressing

KW - Interstitial-free steels

KW - Mechanical properties

KW - Microstructure

UR - http://www.scopus.com/inward/record.url?scp=79959354106&partnerID=8YFLogxK

U2 - 10.1016/j.msea.2011.05.014

DO - 10.1016/j.msea.2011.05.014

M3 - Article

AN - SCOPUS:79959354106

VL - 528

SP - 6573

EP - 6583

JO - Materials Science and Engineering A

JF - Materials Science and Engineering A

SN - 0921-5093

IS - 21

ER -