Assessing texture development and mechanical response in microscale reverse extrusion of copper
- PDF / 1,187,893 Bytes
- 11 Pages / 584.957 x 782.986 pts Page_size
- 30 Downloads / 171 Views
Yooseob Song and George Z. Voyiadjis Civil and Environmental Engineering Department, Louisiana State University, Baton Rouge, Louisiana 70803, USA
Wen Jin Menga) Mechanical & Industrial Engineering Department, Louisiana State University, Baton Rouge, Louisiana 70803, USA (Received 29 August 2017; accepted 22 January 2018)
Axisymmetric reverse extrusion experiments were conducted on annealed Cu rod specimens to form cup-shaped structures with sidewall thicknesses ranging from ;400 lm down to ;25 lm. Changes in Cu grain morphology, size, and texture were examined through scanning electron microscopy and electron backscatter diffraction (EBSD). Pole figure and orientation distribution function analysis of EBSD data showed the same texture components in the present small-scale metal forming experiments as those observed in macroscale sheet metal rolling. The plastic deformation became inhomogeneous as the characteristic dimension for extrusion decreased to ;25 lm, such that the deformation process involved a small number of Cu grains. Extrusion force–punch displacement curves were measured as a function of extruded cup sidewall thickness and compared to outputs of a continuum plasticity finite element analysis in corresponding geometries. The present work illustrates materials characteristics in small-scale metal forming and suggests directions of future work for bringing improved correspondence between experimentation and modeling.
I. INTRODUCTION
The continuing trend of device miniaturization has motivated studies on microengineering.1 In addition to the design, assembly, and modeling/analysis components, microengineering encompasses a broad range of fabrication technologies, including micromechanical machining,2 microelectrical discharge machining,3 laser beam machining,4 and microforming.5 While the first three fabrication processes are serial in nature, in which the formation of a desired shape/structure takes numerous sequential cuts to achieve, forming is typically a parallel process in which a desired shape/structure is achieved in one or a few steps. To form metal-based microscale shapes/structures with sufficient geometrical simplicity, microforming can achieve higher throughput and lower cost and is thus of current interest. The presence of various mechanical size effects in microforming complicates straight forward extension of macroscale forming down to the sub-mm/micron scales. Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.22
Such mechanical size effects also make the prediction of forming behavior more difficult. Out of the four elements of a microforming system, namely materials, processes, tools, and machines,5 materials behavior during forming at the sub-mm to micron scales is a key factor in determining forming success. Microforming experiments, similar to their macroscale counterparts, typically involve plastic deformation to large strains. While numerous studies have documented changes in materials’ grain structure and
Data Loading...
