Enhanced tensile property at high strain rate of a wire arc additive manufactured high-strength low-alloy steel versus the conventional casting counterpart

Abstract

A comparative study on the tensile performances at the quasi-static and dynamic strain rates between the wire arc additive manufacturing (WAAM) high-strength low-alloy (HSLA) steel and the casting one was carried out. The as-deposited steel performed a synchronously enhanced tensile strength and total elongation at the high strain rate of 100 s⁻¹ versus the lower rate of 0.001 s⁻¹. To explore the underlaying mechanisms for the mechanical properties enhancement, the quasi-static and dynamic deformation behaviors were characterized by electron microscope and synchrotron X-ray diffraction. During the high-strain-rate stretching of the as-deposited steel specimen, the bainitic ferrite (BF) and the retained austenite (RA) deformed more coordinately resulting in lower density dislocations in the deformed BF grains. Furthermore, it was also observed that the high-strain-rate stretching induced dislocation cross slipping in the BF grains, thus leading to the generation of the nanoscale dislocation cells, this played an important role in enhancing the dynamic mechanical performance.