Microstructural evolution and mechanical properties of a 5052 Al alloy with gradient structures
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Microstructural evolution and mechanical properties of a 5052 Al alloy with gradient structures Yusheng Li,a) Lingzhen Li, Jinfeng Nie, Yang Cao, and Yonghao Zhao Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
Yuntian Zhub) Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; and Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA (Received 5 May 2017; accepted 13 July 2017)
In this paper, we report on the microstructural evolution and mechanical properties of a 5052 Al alloy processed by rotationally accelerated shot peening (RASP). A thick deformation layer of ;2 mm was formed after the RASP process. Nano-sized grains, equiaxed subgrains, and elongated subgrains were observed along the depth of the deformation layer. Dislocation accumulation and dynamic recrystallization were found primarily responsible for the grain refinement process. An obvious microhardness gradient was observed for all of the samples with different RASP processing parameters, and the microhardness in the top surface of 50 m/s-5 min RASP-processed sample is twice that of its coarse-grained (CG) counterpart. The yield strengths of the RASP-processed 5052 Al alloy samples were 1.4–2.6 times that of CG counterparts, while retaining a decent ductility (25–84% that of CG). The superior properties imparted by the gradient structure are expected to expand the application of the 5052 Al alloy as a structural material.
I. INTRODUCTION
5052 Al alloy is a typical 5xxx Al–Mg alloy in industrial applications and has been widely used due to its high specific strength, excellent corrosion resistance, and good formability. However, its relatively low strength limits its application.1 Severe plastic deformation (SPD) techniques,2–4 such as accumulative roll bonding (ARB),5,6 equal channel angular pressing (ECAP),7–11 and high pressure torsion (HPT),12,13 have been extensively used to process metals, including Al and Al alloys with ultrafine grains (UFGs, grain size below 1000 nm).14 The strength of these SPD-processed materials can be improved significantly by grain refinement and/or by introducing some specific structures such as nanotwins, stack faults, and nonequilibrium grain boundaries.15,16 For the 5052 Al alloy, microstructures formed during the SPD processes11,17–23 mainly consist of elongated and equiaxed UFGs, dislocation Contributing Editor: Lei Lu a) Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/editor-manuscripts/. A previous error in this article has been corrected. For details, see 10.1557/jmr.2017.459 DOI: 10.1557/jmr.2017.310
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