Improvement of mechanical properties for Zn-Al alloys using equal-channel angular pressing

Multi-pass equal-channel angular Pressing (ECAP) was applied to a commercially used zinc-aluminum alloy (ZA-12) at a temperature of about 75 degrees C by using route B-c, where the sample is rotated by 90 degrees along its longitudinal axis between adjacent passes. The strength, hardness and ductility of the alloy processed by ECAP were investigated as a function of number of passes. In addition, variations in the applied load during pressing through the die were analyzed and the relationship between maximum pressing load and strength of the alloy was established. It was observed that the mechanical properties (mainly strength and ductility) were improved after ECAP processing. It was also observed that the tensile strength and the maximum pressing load showed similar trends with number of passes. The improvement in mechanical properties is mainly attributed to both refined microstructure and high density of dislocations that may occur during ECAP Since this method of severe plastic deformation leads to an increase in both strength and ductility even after a single pass through the die, it is concluded that ECAP provides a simple and effective processing procedure for improving the mechanical properties of Zn-Al alloys. With these improved properties, Zn-Al alloys can be potentially used in new engineering applications. (c) 2005 Elsevier B.V. All rights reserved.