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.
Microstructural characterisation of a Ni–Fe-based superalloy by in situ small-angle neutron scattering measurements
The microstructural evolution at high temperatures was studied in an experimental Ni–Fe-based superalloy DT706 by in situ small-angle neutron scattering (SANS). Modifying the alloy heat treatment to improve the microstructural stability and mechanical properties in Inconel 706 type superalloys has been a significant research goal for many years. The earlier studies of phase transformation relied mostly on optical and electron microscopy investigations of samples that were cooled down to room temperature after the high-temperature exposure. However, the kinetics of γ′ and γ′′ precipitation is very fast and new precipitation does occur during the cooling phase. So it is unlikely that the high-temperature microstructure is retained at room temperature. In this presentation, we followed the phase transformation in DT706 alloy by studying the microstructural changes occurring at elevated temperatures. The results of in situ SANS measurements are presented. Microstructure examination on differently heat-treated samples by electron microscopy gives complementary information on the phase transformation sequences. The formation and evolution of precipitates are strongly influenced by the cooling rate from the solution to the η stabilization temperature. The microstructure of DT706 alloy can be tuned using the in situ SANS results.
Target of inhibition by the anti-lipogenic antibiotic cerulenin of sterol synthesis in yeast.
Abstract The antibiotic cerulenin inhibited the incorporation of 14 C-acetyl-CoA by 67% at a concentration of 9 × 10 −6 M but not that of 14 C-HMG-CoA into the non-saponifiable fraction in a cell-free extract of Saccharomyces cerevisiae . Cerulenin markedly inhibited the activity of partially purified HMG-CoA synthase. No inhibition of acetoacetyl-CoA thiolase activity was observed in the same preparation of HMG-CoA synthase. Therefore, cerulenin inhibition of overall sterol synthesis may be accounted for by the specific inhibition of HMG-CoA synthase activity.