@article {2201, title = {Strength vs temperature for refractory complex concentrated alloys (RCCAs): A critical comparison with refractory BCC elements and dilute alloys}, journal = {Acta Materialia}, volume = {266}, year = {2024}, pages = {119692}, abstract = {

To support the development of refractory complex, concentrated alloys (RCCAs), a clear understanding of the effect of temperature on strength is needed. Body-centered cubic (BCC) refractory metals and dilute refractory alloys show a strong temperature dependence of yield stress (\σy) at low and high temperatures, with a relatively temperature-independent regime in between. RCCAs may introduce important changes in deformation and strengthening mechanisms, so it is not clear if RCCAs will show the same thermal dependencies. The objective of this work is to answer the question, \“Is the temperature dependence of strength similar or different for RCCAs compared to BCC refractory elements and dilute refractory alloys ?\” We evaluate \σy vs. temperature for 61 RCCAs by analyzing data curated from the literature. We find that \σy increases progressively from refractory BCC elements, to dilute alloys, to single- and multi-phase RCCAs. Single-phase RCCAs show the same three thermal regimes, but the stresses are higher and the intermediate plateau is shorter and is sometimes steeper. The thermal dependence of \σy in multi-phase RCCAs shows more substantial differences. Six factors that contribute to the higher \σy of RCCAs are discussed: (i) higher solute concentration; (ii) dispersion in atomic sizes; (iii) the shear modulus magnitude; (iv) the type of principal elements; (v) the solvus temperature of predicted secondary phases; and (vi) microstructure. Based on the present observations and analyses, suggestions for future research are made, especially regarding improved models for the effect of temperature on strength.

}, keywords = {High-entropy alloys, Refractory complex concentrated alloys (RCCAs), Temperature effects, Yield strength}, issn = {1359-6454}, doi = {https://doi.org/10.1016/j.actamat.2024.119692}, url = {https://www.sciencedirect.com/science/article/pii/S1359645424000454}, author = {D.B. Miracle and O.N. Senkov and C. Frey and S. Rao and T.M. Pollock} } @article {1631, title = {Growth accidents induced by primary γ' precipitates in a polycrystalline nickel-based superalloy}, journal = {Scripta Materialia}, volume = {186}, year = {2020}, month = {09/2020}, pages = {109-113}, abstract = {

The development of overgrown grains during sub-solvus annealing of a polycrystalline\ \γ\−\γ\′\ nickel-base alloy is investigated, with special emphasis on the primary\ \γ\′ precipitates. Quantitative analysis conducted on a large three-dimensional electron back-scattered diffraction dataset reveals a high fraction of\ \γ\′ precipitates on the annealing twin boundaries in the large grains. When observed in-situ in a scanning electron microscope, the formation of annealing twins is correlated to the crossing of\ \γ\′ precipitates by moving grain boundaries. The role of precipitates in the occurrence of growth accidents is discussed.

}, keywords = {3D EBSD, Annealing twin boundaries, Critical recrystallization, Nickel-base superalloy, Recrystallization}, doi = {https://doi.org/10.1016/j.scriptamat.2020.05.020}, url = {https://www.sciencedirect.com/science/article/abs/pii/S1359646220302979$\#$fig0005}, author = {M.A. Charpagne and A.T. Polonsky and M.P. Echlin and S. Jacomet and J. de Jaeger and M. De Graef and N. Bozzolo and T.M. Pollock} } @article {1626, title = {Measurement of elastic and rotation fields during irreversible deformation using Heaviside-digital image correlation}, journal = {Materials Characterization}, volume = {169}, year = {2020}, month = {11/2020}, pages = {110600}, abstract = {

The recent development of the high resolution and discontinuity-tolerant digital image correlation technique enables the extraction of discontinuities within a displacement field. The technique provides quantitative analysis of discontinuities arising from slip, shear bands, cracks, and grain boundary sliding in a variety of material systems, including polycrystalline metallic materials. The discontinuity-tolerant digital image correlation method can be implemented to retrieve not only quantitative discontinuity analysis but also the local strain and rotation fields that operate near these discontinuities. The present implementation includes high-resolution digital image correlation (HR-DIC) measurements collected in a scanning electron microscope for analysis of both the plastic and elastic fields that develop during deformation of polycrystalline metallic materials. The combination of the discontinuity-tolerant DIC technique with the computation of internal gradients enables extraction of non-localized strain and rotation fields during plastic deformation of a nickel-based superalloy. Therefore the lattice rotation/expansion and plastic localization that occur during deformation can be determined in a single experiment. This method is validated using synthetic images with preset deformation, and experimental measurements using the electron back scatter diffraction (EBSD) technique.

}, doi = {https://doi.org/10.1016/j.matchar.2020.110600}, url = {https://www.sciencedirect.com/science/article/abs/pii/S1044580320320714}, author = {J.C. Stinville and M.A. Charpagne and F. Bourdin and P.G. Callahan and Z. Chen and M.P. Echlin and D. Texier and J. Cormier and P. Villechaise and T.M. Pollock and V. Valle} }