Mechanical properties of wire arc additively manufactured steels at polar temperatures

Abstract

Wire arc additive manufacturing (WAAM) offers the potential for automated construction in remote locations such as in polar regions, where the climate is cold and harsh and labour is scarce. To facilitate such applications, an experimental study into the mechanical properties of WAAM steel plates at polar temperatures has been conducted. Following microstructural and geometric characterisation, 48 as-built and machined WAAM tensile coupons made of normal and high strength steel wires were tested in the temperature range of −100 ℃ to 20 ℃. The low temperature environment was achieved by means of a liquid nitrogen cooling chamber, while the deformations of the coupons were monitored using digital image correlation (DIC). The stress-strain curves and key mechanical properties of the WAAM material are presented and discussed. It is shown that the Young’s modulus, strength and ductility of the WAAM steels increased with decreasing temperature to varying degrees, with the clearest ascending trend observed for the ultimate strength. Fractography was carried out on the tested coupons, revealing principally ductile fracture at low temperatures, though coupled with somewhat brittle features. Finally, predictive equations that can accurately capture the low temperature mechanical properties of the WAAM steels are proposed.