Applications of nuclear reaction analysis for determining hydrogen and deuterium distribution in metals

The use of ion beams for materials analysis has made a successful transition from the domain of the particle physicist to that of the materials scientist. The subcategory of this field, nuclear reaction analysis, is just now undergoing the transition, particularly in applications to hydrogen in materials. The materials scientist must locate the nearest accelerator, because now he will find that using it can solve mysteries that do not yield to other techniques. 9 figure

Research on hydrogen effects on phase distribution ahead of propagating cracks in stainless steel. Final report

This research was performed in support of computations to determine the distribution of hydrogen at a crack tip in an unstable stainless steel. It involved metallographic observations of the distribution of martensite at a stressed crack tip. It is concluded that the martensite phase distribution is much too fine to model realistically by the finite element method when far-field stress effects must be included. The mesh size would have to be less than 50 micrometers in order to include the effects of non-uniform distribution of martensite within a single grain. This would lead to unrealistic computation times. A reasonable compromise is to assume that a finite element will be considered to change from the hydrogen diffusivity of the austenite to that of the bcc martensitic phase when the yield stress of the austenite has been reached. This should give a significantly different hydrogen distribution from the case of untransforming austenite and allow the FEM computations to verify or disprove the kinetic model of hydrogen embrittlement of unstable austenitic stainless steels

Study of diffusion of oxygen in dilute vanadium alloys using solid electrolytic cells

The bulk diffusivity of oxygen has been measured as a function of temperature in dilute vanadium alloys. The emf vs time is measured on the electrolytic cell: Pt/Nb+NbO/ThO/sub 2/-7%Y/sub 2/O/sub 3//V-alloy/Zr/Pt. The oxygen content, which is initially uniform in the vanadium-based alloy, drains into the zirconium sink as a function of annealing time. After a short transient, the rate of cell emf change is directly proportional to the diffusivity of oxygen in the alloy. Substitutional solutes in vanadium have been chosen on the basis of their atomic sizes in vanadium and the heats of formation of their oxides. Oxygen diffusion results have been obtained for nickel, chromium, niobium, tantalum, titanium, zirconium and hafnium as binary solute additions of up to 4 at. %. The oxygen diffusivity results are compared with those for niobium-based alloys. Interpretations of the results are made using two models for the thermodynamics and kinetics of trapping of interstitial atoms by substitutional solute atoms