Hydrogen Diffusion Influence on the Stabilizing Phases Behavior in the Ti-6Al-4V Alloy

For obtaining a unique microstructure in Ti-6Al-4V, hydrogen is utilized as a temporary alloying element; therefore, the mechanism of hydrogen diffusion in α and β phases should be understood. In this study, the electrochemical hydrogenation was applied to the half-length of thin titanium rods, and the diffusion annealing heat treatment was implemented at different temperatures. The hydrogen diffusion coefficient of α phase (Dα) and the hydrogen diffusion coefficient of β phase (Dβ) was determined by employing Abaqus software and C# program for three different homogeneous microstructures. The obtained results showed that Dβ increases, and Dα decreases when the hydrogen concentration in β phase increases. Furthermore, it was observed that each microstructure has a specific temperature in which the maximum hydrogen amount is absorbed. The hydrogen uptake depends more on the volume fraction of β phase than the volume fraction of α phase, which is considered an obstacle to hydrogen diffusion in this alloy.

Contact Surfaces Preparation in Manufacturing of Bimetallic Strips CuZn10 Brass - C22E Steel - CuZn10 Brass

Contact surfaces preparation before cold cladding is one of the most important technological operations. A joint plastic components deformation of the of bimetal 1 according to OST 3-6648-91 and bimetal 3 according to OST 3-6649-91 CuZn10 brass - C22E steel - CuZn10 brass (according to EN standard) should be performed with the strongest possible compression to obtain the required layers connection strength, ensuring strip winding into a roll without delamination. We investigated influence of some factors on the bond strength of bimetal layers: surface hardening of contact surfaces, presence of an underlayer on a steel base, contact surfaces micro geometry, components heating temperature in the deformation zone, diffusion annealing after cladding and a bimetal layers thicknesses ratio effect. Cold cladding technological recommendations have been developed for manufacturing of bimetal 1 according to OST 3-6648-91 and bimetal 3 according to OST 3-6649-91 (CuZn10 brass - C22E steel - CuZn10 brass).

A mechanism with severing near barbed ends and annealing explains structure and dynamics of dendritic actin networks

Single molecule imaging has shown that part of actin disassembles within a few seconds after incorporation into the dendritic filament network in lamellipodia, suggestive of frequent destabilization near barbed ends. To investigate the mechanisms behind network remodeling, we created a stochastic model with polymerization, depolymerization, branching, capping, uncapping, severing, oligomer diffusion, annealing, and debranching. We find that filament severing, enhanced near barbed ends, can explain the single molecule actin lifetime distribution, if oligomer fragments reanneal to free ends with rate constants comparable to in vitro measurements. The same mechanism leads to actin networks consistent with measured filament, end, and branch concentrations. These networks undergo structural remodeling, leading to longer filaments away from the leading edge, at the +/- 35$^o$ orientation pattern. Imaging of actin speckle lifetimes at sub-second resolution verifies frequent disassembly of newly-assembled actin. We thus propose a unified mechanism that fits a diverse set of basic lamellipodia phenomenology.

Effect of radiation exposure on the structure and diffusion in the near-surface layer of ultrafine-grained nickel

The effect of irradiation with a pulsed electron beam (PEB) in the mode of surface melting absence on the copper diffusion in the near-surface layer of ultrafine-grained (UFG) nickel has been studied. The profiles of the copper concentration distribution over depth after isothermal diffusion annealing and annealing under PEB irradiation of the UFG nickel surface are determined. It has been established that as a result of PEB irradiation, the coefficient of grain-boundary diffusion of copper in nickel increases and the mode of grain-boundary heterodiffusion changes in the near-surface layer of nickel in comparison with isothermal diffusion annealing.

Evolution of the structure and grain boundary ensemble of nickel during diffusion annealing under conditions of a segregating impurity (silver) along grain boundaries

Investigations of the effect of an impurity (silver) segregating along the grain boundaries of nickel on the evolution of the structure and grain-boundary ensemble under conditions of diffusion annealing at a temperature of 823 K for 6 hours have been carried out. It is shown that, under these conditions, the development of a diffusion-induced recrystallization (DIR) process is observed in the Ni(Ag) system, in contrast to the Ni(Cu) system, in which the process of diffusion-induced grain boundary migration (DIGM) was observed. The estimates made have shown that a possible reason for the fact that diffusion-induced migration of grain boundaries practically does not occur in the Ni(Ag) system can be significantly lower than in the Ni(Cu) system the value of osmotic pressure as the driving force for the DIGM process.

Production of pure nickel alloys doped with sulfur and phosphorus

A procedure for alloying nickel with sulfur and phosphorus by diffusion and homogenizing annealing is described using the example of pure nickel (RRR at 600). A scheme of the installation for alloying from the gas phase is described. The possibility of uniform alloying with sulfur and phosphorus of samples and material in the form of plates or foils with a thickness of 0.2 mm or thinner at a concentration ranging between 0.001 and 0.08) at. % is shown. Diffusion annealing is carried out after heating and pumping out in a high vacuum and without contamination, in a quartz volume containing sulfur or phosphorus vapors at a temperature of 1100 to 1200 °C. By choosing the ratio of the masses of the alloyed material and the corresponding filling of sulfur or phosphorus, it is possible to predict in advance the resulting concentration of impurities with a sufficient time of annealing. The impurity concentration is uniform in volume within ten percent. Modeling and control annealings with the measurement of the residual resistivity of the control samples allows you to evaluate the results obtained.