Micromechanical and microstructure analysis of strain-induced phenomena in ultrasonic additively-manufactured Al-6061 alloy

Abstract

This work investigates the anisotropic mechanical behavior (both macro and micro) of Al6061 alloy samples manufactured using ultrasonic additive manufacturing. Samples from both sonotrode travel and vibration directions (TD and VD, respectively) were investigated in the as-built and aged (8 h at 180 °C under Argon gas) conditions. The aged VD-specimens showed appearance and propagation of Luders-like band, which did not exist in the TD-specimens, deformed at the same strain rate. X-ray diffraction, x-ray computed tomography, scanning electron microscopy, laser flash technique and in-situ loading with neutron diffraction were used to characterize the material and its hardening behavior during straining. Aging was mainly found to lead to relaxation of stresses, induced by the build process, some decrease in yield stress, and potential secondary phase reprecipitation. Stress partitioning, revealed via in situ neutron diffraction, showed that one of grain families, (110) || tensile axis, revealed strain softening at small strain range. This texture component, (110) || tensile axis, dominated the structure of VD-specimens, and was one of key factors stimulating band appearance and propagation.