Gradient microstructure and texture in wedge-based severe plastic burnishing of copper
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Saurabh Basu The Harold and Inge Marcus Department of Industrial and Manufacturing Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Tejas G. Murthy Department of Civil Engineering, Indian Institute of Science, Bangalore 560012, India
Christopher Saldanaa) The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta 30332, Georgia (Received 18 December 2017; accepted 2 March 2018)
In the present study, gradient microstructure and texture development in wedge-based severe plastic burnishing of oxygen-free high conductivity copper was investigated. Microstructural response and evolution of crystallographic texture in severe surface plastic deformation was shown to be controllable in terms of both magnitude and gradient through control of the incident wedge angle and burnishing parameters. Equiaxed ultra-fined grains and micro/nanoscale elongated grains were produced in the subsurface region, which is indicative of dynamic recrystallization at large strains in the subsurface. Subsurface regions exhibited a significant fraction of shear texture components along the h110i partial fibers. Texture evolution simulated using the visco-plastic self-consistent framework revealed variations in strain level controlling different mechanisms for rotation of these partial fibers from their ideal orientation. Controllability of subsurface properties and microstructure for such materials is briefly discussed. These results allude to fundamental limits in material processing by severe shear using scalable deformation configurations. I. INTRODUCTION
The endowment of gradients to near-surface microstructures in machine elements has garnered significant interest recently. This interest originates from strong correlations between these gradients and concomitant enhancements of surface-originating structural and functional behavior in fabricated components.1,2 For instance, gradients involving near-surface nanocrystalline microstructures on a microcrystalline bulk exhibit enhanced resistance to scratching, fatigue, and corrosion3–5 in addition to featuring superior combinations of ductility and strength compared to homogeneous microstructures featuring a lack of gradients.6 The sources of these unique properties are found in synergetic strengthening created by the incompatible deformation present across the mixture of refined and coarse grains, which result from promoted dislocation activities.7 In this regard,
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.58
materials with gradients in microstructures are more promising candidates for applications where the typical enhanced properties accessible through grain refinement must be attained without an appreciable loss of ductility. Mechanical surface modification techniques involving grain refinement by severe plastic deformation (SPD), viz. surface severe plastic deformation (S2PD), have been developed for fabrication of gr
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