• In situ synchrotron X-ray techniques reveal WAAM Mg alloy deformation dynamics. • In situ multi-scale measurements reveal the alloys weak anisotropy and twin evolution. • In situ 3D imaging shows voids grow and reorient in WAAM Mg alloy. • Temperature impacts WAAM Mg alloy strength, ductility, twinning, and fracture. Deformation dynamics of a wire-arc additively manufactured (WAAM) Mg-3Al-1Zn alloy are investigated via in situ synchrotron computed tomography (CT) and X-ray diffraction along with in situ digital imaging correlation measurements, and postmortem microstructural characterizations. Bulk true stress - strain curves, mesoscale strain fields and microscale X-ray diffraction patterns are obtained simultaneously for tensile loading along the build direction (BD) and the transverse direction (TD). The alloys texture-free, equiaxed microstructure gives rise to the pronounced activation of non-basal slip systems, and limited 10-12 extension twinning. This critical shift in deformation mode from highly anisotropic deformation relying on twinning to more isotropic deformation driven by non-basal slip explains the observed weak anisotropy in its mechanical behavior and stable strain hardening, different from conventional Mg alloys. Our in situ observations further dynamically track the evolution of solidification voids, demonstrating how their initial preferred orientation and subsequent reorientation dictate early ductility and influence damage accumulation mechanisms. Additionally, loading temperature significantly modulates the intricate interplay between these active deformation modes, evolving void morphology, and ultimately the fracture mechanisms. This work provides multi-scale mechanistic insights into how WAAM-specific microstructures, temperature, and defect evolution interact during deformation, providing new insights into the high-performance Mg alloys.
Ye et al. (Sun,) studied this question.