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Twinning-induced large tensile strains in directionally-solidified Fe(1-x)Ga(x) oligocrystals

Published

Author(s)

Nicholas J. Jones, Yared Amanuel, Jazalyn D. Dukes, Paul K. Lambert, Jin-Hyeong Yoo

Abstract

Fe1-xGax alloys require highly textured samples for optimal magnetostrictive performance. This is accomplished through directional solidification techniques, yielding very large grains (≈5 mm) and few grain boundaries in a sample. These oligocrystals have a drastically different microstructure than traditional materials, and render classical strain measurement techniques impractical. In this study, we measure the mechanical properties of commercial Fe81.6Ga18.4 oligocrystals using sub-sized tensile specimens and digital image correlation (DIC). While many samples fractured around 360 MPa (the literature yield/tensile stress), most had discontinuous yielding as low as 186 MPa. Many of the samples also exhibited large tensile strains, up to 5 %, which is uncharacteristic for a generally brittle material, with large specimen-to-specimen variations in the total elongation. In all specimens, DIC showed high strain bands that develop at very defined angles (≈60° from the tensile axis), although fracture in these high- strain regions was surprisingly rare. Electron back-scattered diffraction was performed on specimens to help correlate the observed strain field with the underlying crystallography, and revealed significant deformation twinning.
Citation
Journal of Alloys and Compounds

Keywords

Deformation Twins, Digital Image Correlation (DIC), Iron Alloys, Magnetostriction, Strain, Stress, Galfenol

Citation

Jones, N. , Amanuel, Y. , Dukes, J. , Lambert, P. and Yoo, J. (2021), Twinning-induced large tensile strains in directionally-solidified Fe(1-x)Ga(x) oligocrystals, Journal of Alloys and Compounds, [online], https://doi.org/10.1016/j.jallcom.2021.158738 (Accessed September 23, 2021)
Created January 12, 2021, Updated May 4, 2021