On the Achievement of Nanostructured Interstitial Free Steel by Four-Layer Accumulative Roll Bonding Process at Room Tem
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GRAIN size is a key microstructural factor affecting mechanical properties of materials.[1–3] The most important effect of grain size reduction is an increase of the yield strength. A higher yield strength makes it possible to reduce the mass of a structural element for bearing the same load; that is, weight lightening can be achieved by using nanostructure and ultrafine grain (UFG) materials for structures. Therefore, grain refinement has attracted considerable interest from metal engineering scientists.[1–7] Severe plastic deformation (SPD), a top–down approach that applies intense strains to workpiece materials, can be used for the production of bulk, fully dense nanostructured and UFG materials.[1–7] In this context, well-established techniques are high-pressure torsion (HPT), equal-channel angular pressing (ECAP), and accumulative roll bonding (ARB).[1–7] However, the
ROOHOLLAH JAMAATI, Assistant Professor, is with the Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran. Contact e-mails: [email protected]; [email protected]; [email protected]. MOHAMMAD REZA TOROGHINEJAD and HOSSEIN EDRIS, Professors, are with the Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran. SAJJAD AMIRKHANLOU, Independent Researcher, is with the Young Researchers and Elite Club, Najafabad Branch, Islamic Azad University, Najafabad, Iran. Manuscript submitted November 28, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
HPT and ECAP processes are discontinuous techniques with a limited material output. The ARB process is the most appropriate for fabrication of sheet materials and has an advantage for mass production because it can be carried out easily using conventional rolling apparatus. Additionally, it can supply semifinal products in the form of sheets that can be directly used for further work forming operations.[3,7] Metal matrix composites,[8–13] aluminum,[7,14–17] copper,[18] brass,[19] and steel[20–23] are some examples of materials that have been produced by the ARB process. So far, efforts have been made to achieve nanostructure in the interstitial free (IF) steel via the ARB process, but none of the researchers have managed to create a nanostructure in this steel. The minimum grain size of SPD methods applied on the IF steel by different researchers was about 300 nm.[20–25] To achieve nanostructure in the IF steel by the ARB process, one strategy that can be effective is preventing the easy movement of dislocations and occurrence of extended recovery by deformation at room temperature. It should be noted that in the previous research, the ARB process was performed at elevated temperature.[20–25] Recently, the current authors investigated the mechanical properties of IF steel fabricated by the ARB process at room temperature.[26] However, the current work is, to the best of our knowledge, the first of its kind that focuses on the microstructural evolution of the IF steel sheets processed by ARB process at room temperature.
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