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

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°. 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°, 110° and 135° 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.