The impact resistance of silicon (Si)-containing modified 9Cr-1Mo steels has been investigated within a temperature regime of 240 to 440°C using the Charpy method. The results indicate that the energies absorbed in fracturing the tested specimens were substantially lower at temperatures of 240, 25, and 75°C compared to those at elevated temperatures. Lower impact energies and higher ductile-to-brittle-transitiontemperatures (DBTTs) were observed with the steels containing 1.5 and 1.9 wt.% Si. The steels containing higher Si levels exhibited both ductile and brittle failures at elevated temperatures. However, at lower temperatures, brittle failures characterized by cleavage and intergranular cracking were observed for all four tested materials.
I -Gas desorption and positron annihilation techniques have been employed to study@ $ *F metals has a rather high affinity to vacancy type defects. The results obtained for low irradiation dose show that substitutional nitrogen (NV; with V-vacancy) is formed. The nitrogen vacancy complex dissociates at temperatures ranging from 350 K for Ni to 900K for Mo and 1 100 K for W. At high doses defects are fonned which can be characterized as nitrogen saturated vacancy clusters. These defects, as observed by helium probing, disappear during annealing for nickel at SOOK, and for Mo at 1100 K. The direct observation of the desorbing nitrogen for nickel and molybdenum reveals a very fast desorption transient at the dissociation temperature of the clusters. This is the characteristic desorption transient of a small nitride cluster,e,g., by shrinkage with constant rate. For iron the nitrogen desorption is more complicated because of a general background that continuously rises with temperature. With the positron beam technique depth information was obtained for defects in iron and the defect character could be established with the help of the information provided on annihilation with conduction and core electrons of the defect trapped positrons.nitrogen associated defects in nitrogen irradiated metals: Fe, Ni, Mo and W. Nitrogen O in T O f t ese
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.