Formation and Dissolution of γ’ Precipitates in IN792 Superalloy at Elevated Temperatures
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.
Temperature-dependent compression behavior of an Al0.5CoCrCuFeNi high-entropy alloy
Abstract Mechanical response of an Al0.5CoCrCuFeNi high-entropy alloy (HEA) was investigated through uniaxial compression tests, the 0.2% offset yield strength decreases with increasing temperature up to 773 K. However, at temperatures above 773 K, two yield strength hardening regions peaked at 873 K and 1073 K were observed. Microstructure analyses reveal an enhanced L12 ordering with the increase of compression temperatures and the subsequent precipitation of B2 phase at 973 K. Meanwhile, transmission electron microscopy observations of the post-deformation microstructures show that plastic deformation is primarily carried by dislocation at room temperature, and changes to twinning at temperatures higher than 873 K. At deformation temperatures higher than 1073 K, a mixed microstructure of dislocations and deformation twins is observed. These results suggest that the emerging of the yield strength peaks at high temperatures is related to the precipitation of the L12 and B2 intermetallic phases and high-temperature deformation influences the phase separation and phase selection of the HEA.
Magnetic properties of Lu2Fe17 crystals
Abstract We present the results of crystal structure and magnetization studies of three single crystals grown from melts of different nominal compositions in the vicinity of the Lu2Fe17 stoichiometry. The ferromagnetic state of the crystals is strongly dependent on the real sample composition and the local atomic ordering. A drastic difference is observed in the behaviour of the ferro–antiferromagnetic transition, even in crystals for which almost identical composition and crystal parameters were determined by microprobe and X-ray analysis.