Analysis of the milli-forming of single-crystal and poly-crystal bar

Abstract

This paper is concerned with the analysis of the milli-forming process, which forms milli-size products. Since the size of the workpiece in a milli-forming process ranges from a few hundred micrometers to a few millimeters, microstructural changes such as the growth of micro-voids and the development of preferred orientation in a grain become crucial factors for the success of milli-forming. In the proposed finite element model, anisotropy from deformation texture and the deterioration of mechanical properties due to the growth of micro-voids are coupled in the virtual work expressions for momentum and mass balance. Two extreme cases of a milli-bar, one made up of a single crystal and the other of poly-crystals or a large number of grains, are chosen for the simulations of extrusion/drawing. The predicted results are carefully examined in terms of extrusion/drawing forces, preferred orientations, and damage evolution in order to understand the deformation characteristics of a milli-bar.