The processing of difficult-to-work alloys by ECAP with an emphasis on magnesium alloys

摘要

The equal-channel angular pressing of pure metals is conducted most expeditiously by pressing at room temperature using a die with a channel angle of 90 degrees. However, these conditions may lead to cracking of the billets or massive segmentation when applied to hard and difficult-to-work alloys. This paper uses finite element modeling to explore the procedures for successfully pressing these more complex materials. Separate models are developed using channel angles of 90 degrees, 110 degrees and 135 degrees for materials having strain rate sensitivities of 0, 0.2 and 0.4. The calculations show that cracking and segmentation may be reduced or eliminated by increasing the strain rate sensitivity and/ or increasing the channel angle within the die. The magnitude of the imposed damage is evaluated for each condition using a macroscopic damage criterion. It is demonstrated that the predicted results are in good agreement with experimental data obtained using a ZK60 magnesium alloy. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.