Boron largely increases the ductility of polycrystalline high-temperature Co-Re-Cr alloys. Therefore, the effect of boron addition on the alloy structural characteristics is of large importance for the stability of the alloy at operational temperatures. Along with the Co-solid solution matrix phase transformation from hcp to fcc structure, additional structural effects were observed in situ at very high temperatures (up to 1500 • C) using neutron diffraction (ND) in boron-containing Co-17Re-23Cr alloys. Increasing boron content up to 1000 wt. ppm lowers the temperature at which sublimation of Co and Cr from the matrix occurs. As a result, the composition of the matrix in the surface region is changed leading to the formation of a second and a third matrix hcp phases at high temperatures. The consideration on the lattice parameter dependence on composition was used to identify the new phases appearing at high temperatures. Energy-dispersive spectroscopy and ND results were used to estimate the amount of Co and Cr which sublimated from the surface region of the high-boron sample. In the sense of alloy development, the sublimation of Co and Cr is not critical as the temperature range where it is observed (≥1430 • C) is significantly above the foreseen operation temperature of the alloys (1200 • C).
We studied the effect of short fibers on the mechanical properties of a magnesium alloy. In particular, deformation mechanisms in a Mg-Al-Sr alloy reinforced with short alumina fibers were studied in situ using neutron diffraction and acoustic emission methods. The fibers' plane orientation with respect to the loading axis was found to be a key parameter, which influences the acting deformation processes, such as twinning or dislocation slip. Furthermore, the twinning activity was much more significant in samples with parallel fiber plane orientation, which was confirmed by both acoustic emission and electron backscattering diffraction results. Neutron diffraction was also used to assist in analyzing the acoustic emission and electron backscattering diffraction results. The simultaneous application of the two in situ methods, neutron diffraction and acoustic emission, was found to be beneficial for obtaining complementary datasets about the twinning and dislocation slip in the magnesium alloys and composites used in this study.
Precipitation of γ' phase in nickel-base superalloy IN792-5A was studied using in-situ Small Angle Neutron Scattering (SANS). It was found that additional precipitates are formed after reheating above 600˝C when the material is previously fast cooled (100 K/min) from 900˝C. The size distribution and volume fraction of the additional γ' precipitates as well as of the already present medium-size precipitates in dependence on temperature were evaluated. The small precipitates can influence mechanical properties of the alloy, which exhibits an anomaly in the temperature dependence of the yield stress. Volume fraction of all precipitate populations above 900˝C was estimated as well.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.