Investigating the role of processing temperature on the microstructure evolution, mechanical properties, and corrosion behaviour of equal channel angular pressed AZ31 Mg alloy

Abstract

AZ31 magnesium (Mg) alloy was subjected to equal channel angular pressing (ECAP) through Bc route at three different temperatures (200, 250 and 300 °C) to investigate the role of processing temperature on the microstructure evolution. All the sample were processed for one complete cycle which includes 4 consecutive pressings. Workpiece processed at 200 °C has shown relatively higher grain refinement (2.1 ± 1.4 μm) compared with the samples processed at 250 °C (5.6 ± 2.7 μm) and 300 °C (7 ± 5.5 μm) from a starting size of 36 ± 4.1 μm. Increased hardness was measured for the ECAPed samples at 200 °C due to the higher level of grain refinement. Workpiece produced at 200 °C exhibited higher tensile strength (270.9 ± 6.3 MPa) compared with the other processed samples and base alloy. Surface energy measurements from the contact angles show the positive effect of grain refinement on increasing the hydrophilic nature of AZ31 alloy. Corrosion experiments from the potentiodynamic polarization studies demonstrate lower corrosion current for the base alloy compared with all of the processed alloys. The deteriorated corrosion performance in the ECAPed alloys can be claimed to the increased crystal imperfections due to ECAP. From the results, it is understood that the lower processing temperatures are preferable to achieve higher level of grain refinement in ECAP of AZ31 Mg alloy. Excellent mechanical properties can be achieved in AZ31 alloy by ECAP and the decreased corrosion resistance is a concern to pay more attention.