Localization of plastic strain in alloy 718 using digital image correlation

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Experimental and numerical investigations of nanoindentation properties at the sub- grain level in Ni-based and Ti-based polycrystalline alloys

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TEM preparation technique influence on an LBM AlSi7Mg0.6 alloy nanostructure

To provide detailed characteristics on the laser beam melting AlSi7Mg0.6 alloy, transmission electron microscopy is required as the microstructure is composed of aluminum cells hardened by nano-sized precipitates encapsulated in a 3D silicon structure. However, sample preparation techniques can cause local temperature variation or irradiation that impact the local microstructure. With various thin-foil preparations, we have shown that standard twin jet electropolishing produce thin, well-defined aluminum cells filled with nano-sized precipitates. When ion-based methods are used, due to local heating and irradiation, the nanoprecipitates are significantly altered. Lowering the preparation technique temperature appears to be equivalent to twin jet electropolishing

Strain localization in the Alloy 718 Ni-based superalloy: From room temperature to 650 °C

International audienceIrreversible deformation in relation to the microstructure was investigated for a polycrystalline Ni-based superalloy (Alloy 718) from room temperature to 650 °C using high-resolution digital image correlation (HR-DIC) techniques. Interrupted tensile tests were performed under a protective atmosphere to ensure the stability of the speckle pattern to track kinematics fields from surface analyses. In-plane strain localization was captured using HR-DIC on scanning electron microscopy (SEM) images. A statistical analysis of different strain localization events in relation to the microstructural features was conducted, i.e., intragranular slip localization, slip localization parallel to and near Σ3-twin boundaries (Σ3-TB), and grain boundary sliding (GBS). Alloy 718 exhibited slip localization at room temperature and 350 °C. Intense strain localization develops parallel and in the vicinity of Σ3-TB from the onset of the microplasticity. Few intense slip stimulated-grain boundary sliding events were found due to slip localization on both grains adjacent to the grain boundary. At 650 °C, Alloy 718 experienced grain boundary sliding at the onset of the yield without particular slip localization in adjacent grains. At lower temperatures, strain localization parallel to and near Σ3-TB was intense, and intragranular slip localization intensified with increasing macroscopic deformation. Particular microstructural configurations were found at 650 °C leading to premature damage: (i) sub-surface cavitation at grain boundaries, and (ii) grain boundary cracking due to intense shearing near a Σ3-TB