Deformation mechanics and microstructure evolution during indirect extrusion in (sub) mm-scale samples
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Saurabh Basu Department of Mechanical Engineering, George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30313, USA
M. Ravi Shankara) Department of Industrial Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA (Received 6 August 2015; accepted 18 February 2016)
Mechanics of deformation in miniaturized indirect extrusion (IE) and their resulting process outcomes are shown to be dependent on the dimensional scale of the plastic deformation zone. Using optically transparent dies as prototypes, the effect of process length-scales on the strain, strain-rate, and rotation fields is elucidated using digital image correlation. In this regard, in situ experiments were performed on commercially pure Lead (Pb) and Aluminum (Al 1100) as prototypical nonwork/work hardening materials. By overlaying these measurements with microstructural characterization via electron backscattered diffraction, the effect of deformation volume on process–structure mappings is identified. Herein, visco-plastic self-consistent framework-based modeling of the evolution of crystallographic textures was investigated to achieve insights into the trajectories of microstructure evolution and process outcomes during IE. These findings provide a beneficial background about characteristics of plastic deformation zone and its distribution to optimize and control the properties of miniaturized components.
I. INTRODUCTION
Material response and microstructure evolution in deformation-based manufacturing processes are underpinned by the interplay of the geometric and tribological boundary conditions. Heterogeneity in the mechanics, process instability, and failures also result from this interplay. However, delineation of these linkages is complicated by the material response during fabrication that exhibits hitherto unknown phenomena in the presence of complex geometrical confinement.1 This is particularly an issue for the control of miniaturized deformation-based manufacturing processes. In this regard, direct measurement of the mechanics in the deformation zone, as a function of the process parameters, tribological conditions, microstructure, and material parameters, is useful for identifying the process– microstructure mappings. The thermomechanics of the deformation zone emerges as a function of aforementioned mappings and determines the process outcomes and properties. Empirical [e.g., using digital image correlation (DIC)2], analytical [e.g., using slip line fields (SLFs)3], and numerical (e.g., using finite element Contributing Editor: George M. Pharr a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.85 1096
J. Mater. Res., Vol. 31, No. 8, Apr 28, 2016
methods4) techniques exist for characterizing deformation zone geometries, which are then used to rationalize the evolution of the microstructure and ultimately the product outcomes. However, additional complexities emerge when the scale of deformation becomes smaller, such as in microforming p
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