Material properties of wire arc additively manufactured steel at elevated temperatures

This paper presents an experimental investigation into the material properties of wire arc additively manufactured (WAAM) steel at elevated temperatures. A total of 43 WAAM steel coupon specimens were tested at temperatures ranging from 22 °C (ambient) to 1000 °C. These coupon specimens were extracted from square tubes fabricated using normal strength ER70S-6 and high strength ER120S-G feedstock wires. These specimens were extracted in two directions: parallel and perpendicular to the printing direction. Stress-strain curves were obtained, from which the material properties were extracted, including elastic modulus (E), yield strength (f_y), stress at 2.0 % strain (f_2.0), ultimate strength (f_u), ultimate strain (ε_u), and fracture strain (ε_f). Retention factors for the material properties were calculated by normalizing the values at elevated temperatures to the corresponding values at ambient temperature. The obtained retention factors were compared with those specified in the international steel design codes, including EC 3, AISC 360, AS 4100, and BS5950–8. It is shown that the predicted elastic modulus retention factors (k_E) from EC 3, AISC 360, and AS 4100 are generally conservative, while the predicted yield strength retention factors (k_y) from AS 4100 are generally unconservative for ER70S specimens. The predicted ultimate strength retention factors (k_u) from AISC 360 match well with the test results of ER120S specimens but are unconservative for ER70S specimens. The retention factor curves for material properties of both ER70S and WAAM ER120S steel at elevated temperatures were proposed. Additionally, constitutive models for stress-strain curves of WAAM steel at elevated temperatures were proposed, which are generally accurate when compared to the test results.