A study of plastic deformation behaviour of Ti alloy during equal channel angular pressing with partial back pressure

摘要

Equal channel angular pressing with partial back pressure (ECAP PBP) accumulates large strains in a processed sample, while extruding it through a die with a modified geometry. In order to investigate the deformation behaviour of Ti6Al4V in detail, an ECAP PBP three-dimensional finite element model has been developed using FORGE software. The analysis included the influence of geometry and heterogeneity of plastic deformation. Numerical results showed that partial back pressure, as well as the other modelled factors, significantly affects size and homogeneity of the imposed strain, temperature and stability of material plastic flow. Average value of imposed strain was similar to 1.58. Strain distribution was the most homogenous for the higher friction coefficient; its homogeneity was confirmed by micro-hardness testing. The results show the lowest temperature increase of the billet during ECAP PBP process. Using the partial back pressure, dead zone was eliminated. It also featured the highest reduction of tensile stress when compared to other processes. During the process with partial back pressure, the punch experienced 20% lower load compared to conventional ECAP with back pressure. (C) 2015 Elsevier B.V. All rights reserved.