Effect of cryogenic treatment at different temperatures on microstructure, thermal, mechanical and corrosion response of pure zinc

Abstract

The potential for cryogenic treatment (CT) to enhance properties and performance of metals was first realized with steels, followed more recently with non-ferrous examples such as aluminium and magnesium. A wealth of knowledge on the optimum processing parameters and mechanisms behind the property enhancements has been discovered, and this presents a notable research gap for zinc (Zn) as it has never been explored with CT in the past.

To this end, pure Zn was successfully synthesized using the Disintegrated Melt Deposition (DMD) method, followed by hot extrusion and, for the first time, CT with exposure to varying temperatures (−20 °C, −50 °C, −80 °C, and −196 °C). Densification occurred for all materials (with 39.5 % porosity reduction after exposure to −50 °C being most significant), alongside a further 86.5 % increase in damping capacity after exposure to the same temperature. Microstructurally, CT induced significant grain growth across all exposure temperatures, − 80 °C conferring the largest grains (224 % increase over as-extruded equivalent). Compression response was also improved slightly after exposure to −80 °C, with improvements of 2.7 %, 2.3 %, and 1.0 % to compressive yield strength, ultimate compressive strength, and work of fracture. Exposure to −196 °C also notably lowered corrosion rates (32.4 % reduction). This highlights the ability of CT to not just alter, but tailor individual properties for Zn-based materials and opens up a new research area for this Hexagonal Closed Pack (HCP) metal and its derivatives.