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This work investigates the effects of Ar-based shielding gases on the microstructure and phase balance of duplex stainless steel (DSS) depositions. The results are then used for fabrication of DSS walls using wire arc additive manufacturing (WAAM), and the microstructural characteristics and mechanical performance of the products are assessed. WAAM currently poses as one of the most interesting methods of manufacturing by enabling joining of materials to fabricate structures layer by layer. However, the extreme conditions imposed by the process, such as high heat inputs and re-melt and solidification of the deposited layers, could compromise the performance of the products. A detailed microstructural analysis is conducted on single layer and double layer depositions of DSS to assess the effects of different shielding gases on the ferrite/austenite phase balance in the specimens. The results show that the depositions shielded with a small fraction of carbon dioxide (CO2) present better microstructural features in comparison to depositions shielded with the other selected gases. A mixture of 98%Ar + 2%CO2 was employed for fabrication of a 60-layer DSS WAAM-made wall and some mechanical characteristics were studied. The mechanical examinations demonstrate that the properties of the parts fabricated using WAAM are comparable with their wrought counterparts.

In this study, Wire Arc Additive Manufacturing (WAAM) based Directed Energy Deposition (DED) process is used to build two parts, tube and wall from 2209 Duplex Stainless Steel. Duplex stainless steel is extremely effective against stress corrosion cracking due to existence of an equal portion of austenite and ferrite phases. The challenge is monitoring of the process parameters and cooling rate to promote ferrite phase formation. To this end, three-dimensional transient thermal models of the additive manufactured (AM) parts are presented and the simulated thermal cycles are verified with the experimental results. The correlation between the calculated cooling rates and the phases formation in the WAAM parts is studied and revealed. The results highlight that slow cooling rate of the built layers at elevated temperatures promote austenite formation significantly in a ferrite matrix. Furthermore, the experimental mechanical examinations will illustrate the quality of the WAAM-made parts and compare their mechanical properties with their wrought counter-parts.

In this investigation, composite metal foams were produced by casting aluminum around hollow ceramic spheres arranged in steel mesh structures. This study proposes that “cell arrangement” should be considered as an important parameter in controlling the mechanical properties of CMFs, which can be applied in energy absorber designs. Metal foams with two types of ordered arrangements and relatively similar densities are produced by a novel method and their mechanical properties are examined by compression tests. The results demonstrate that by altering the order of arrangements, the stress–strain performance of samples completely changes. This also results in distinctive brittle and ductile behaviors for the specimens and has significant effects on important factors such as “strength-to-density” and “energy absorption per unit volume” ratios. The interfaces/interphases formed between the components of the composite metal foams were verified by means of scanning electron microscopy method.