Rationalization of anisotropic mechanical properties of Al-6061 fabricated using ultrasonic additive manufacturing

Niyanth Sridharan, Maxim Gussev, Rachel Seibert, Chad Parish, Mark Norfolk, Kurt Terrani, Sudarsanam Suresh Babu

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100 Scopus citations

Abstract

Ultrasonic additive manufacturing (UAM) is a solid-state process, which uses ultrasonic vibrations at 20 kHz along with mechanized tape layering and intermittent milling operation, to build fully functional three-dimensional parts. In the literature, UAM builds made with low power (1.5 kW) exhibited poor tensile properties when loaded along the Z-direction, i.e., normal to the interfaces. This reduction in properties is often attributed to the lack of bonding at the interfaces. The generality of this conclusion is evaluated further in 6061 aluminum alloy builds made with very high power UAM (9 kW). Tensile deformation behavior along X and Z directions were evaluated with small-scale in-situ mechanical testing equipped with high-resolution digital image correlation, as well as, multi-scale characterization of builds. Interestingly, even with complete metallurgical bonding across the interfaces without any discernable voids, poor Z-direction properties were observed. This reduction is correlated to coalescence of pre-existing shear bands at interfaces into micro voids, leading to strain localization and spontaneous failure on tensile loading.

Original languageEnglish
Pages (from-to)228-237
Number of pages10
JournalActa Materialia
Volume117
DOIs
StatePublished - Sep 15 2016

Funding

The aid and technical insight of Kevin Field is gratefully acknowledged. This work was sponsored by Laboratory Directed R&D funds at Oak Ridge National Laboratory . Scanning electron microscopy was performed at Center for Nano phase Materials (CNMS), Oak Ridge National Laboratory , sponsored by the Department of Energy, Office of Basic Energy Sciences . This research was performed, in part, using instrumentation provided by the Department of Energy , Office of Nuclear Energy , Fuel Cycle R&D Program and the Nuclear Scientific User Facilities. The authors also gratefully acknowledge the U.S. Department of Energy , Office of Energy Efficiency and Renewable Energy , Advanced Manufacturing Office .

FundersFunder number
ORNL Laboratory Research and Development Program
U.S. Department of Energy
Office of Energy Efficiency and Renewable Energy
Office of Nuclear Energy
Basic Energy Sciences
Oak Ridge National Laboratory

    Keywords

    • Digital image correlation
    • Electron back scatter diffraction
    • Tensile tests
    • Ultrasonic additive manufacturing

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