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The effects of the prior austenite grain sizes in hydrogen embrittlement of Co-containing 18Ni 300 maraging steel were studied employing Slow Strain Rate Testing (SSRT) in 0.6 M NaCl electrolyte under simultaneuos cathodic polarization. The material was susceptible to hydrogen embrittlement in all investigated conditions. In addition, the examination of the fractured surface revealed that the presence of hydrogen in steel promotes the formation of quasi-cleavage regions and hydrogen-induced cracks along the grain boundaries. However, the refining of the prior austenite grain allowed an improvement in the HE resistance. Moreover, EBSD analysis showed that intergranular cracks propagated along to grain boundaries orientated to {001} planes parallel to normal direction, whereas they were deflected on {101} and {111} crystallographic planes.

Currently, surface treatments lead to inducing a superficial layer of several nanometers up to micrometer, which in some cases can be protective. In this experimental work, an oxide layer was generated under different atmospheres (CO2 and steam atmospheres) during the thermal aging treatment of two different maraging grades, 300 and 350. Afterwards, this layer was microstructural and mechanically characterized by advanced characterization techniques at the micro- and submicron length scale to highlight some information related to the generated oxide layer. The results showed that the oxide layer (in both grades) was made up of several compounds like: TiO2, MoO3, hematite (α-Fe2O3), and CoFe2O4, this being the majority compound distributed homogeneously throughout the layer. Furthermore, a nickel-rich austenitic phase at the interphase was mainly made up cobalt ions (Co2+), instead of iron ions (Fe2+), within the spinel lattice.

The electrochemical behavior of solution-annealed grade 300 and grade 350 maraging steels subjected to two different aging temperatures in an aqueous hydrofluoric acid (HF) medium was evaluated. The microstructural and hardness studies showed the effects of the chemical composition and heat treatments on the material properties. Although it is not possible to observe them, the fine intermetallic composites deposited during aging allow a significant increase in the hardness of materials, which was reduced when aged at 560¿°C, where there was formation of reverted austenite. The results showed that, in both steels, solution-annealed samples that were not aged showed a better corrosion behavior than the aged samples. The reversion of austenite during aging at temperatures above 560¿°C increases the phase limits and its susceptibility to corrosion. The greater amount of cobalt and titanium in grade 350 maraging steel increases the amount of fine intermetallic precipitate rich in molybdenum and titanium during aging, therefore improving its mechanical properties, but also reducing its corrosion resistance.

In this paper, we analyse the quantization of cyclotron orbits for a 2D non-relativistic and spinless charged particle under the influence of a static and uniform magnetic field, the Landau problem. We follow the algebraic approach of rising and lowering operators. The Hamiltonian is expressed in terms of the usual rising and lowering operators of an isotropic quantum oscillator. Through a Bogoliubov transformation, we show that the Hamiltonian may be reduced to the one of a quantum oscillator that accounts for the formation of infinitely degenerate Landau levels. The explicit form of the position-space wave functions of Fock–Darwin states for a vanishing parabolic confinement potential is worked out by applying the techniques of ladder operators and the induction method. To explore the internal dynamics of the electron states, we compute the Fock–Darwin states’ density currents expressing them in terms of the ladder operators. In the supplementary material, we provide the reader with Mathematica algorithm that can help perform some of the calculations exposed in the paper. The charged particle in a magnetic field is used to explore some of the fundamental concepts of quantum mechanics as commuting operators, simultaneous eigenstates, degeneracy, rising and lowering operators, etc. This approach can be used as supplementary material in undergraduate final-year courses like quantum mechanics or solid state physics.

Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows to induce a thin magnetic layer in a mixture of iron, nickel, and cobalt spinel ferrites. On the other hand, the oxide layer presents an adhesive force 99 mN value that shows the capability for being used for tribological applications under sliding contact tests.

We study the internal rotational dynamics of electronic beams in relation to the phase singularities of their wave functions. Given their complex singularity structure, Hermite-Gaussian beams and other superpositions of Laguerre-Gaussian modes are studied here. We show that by inspecting the lowest non-vanishing terms of the wave function near the singularity it is possible to infer the structure of the Bohmian streamlines. Conversely, starting from a map of the electron's Bohmian velocities, we demonstrate that it is possible to derive the form of the electron's wave function near the singularity. We outline a procedure that could yield an experimental method to determine the main parameters of the electron's wave function close to a singularity., Comment: 16 pages, 17 figures, 1 table

We develop a Lie algebraic approach to systematically calculate the evolution operator of the generalized two-dimensional quadratic Hamiltonian with time-dependent coefficients. Although the development of the Lie algebraic approach presented here is mainly motivated by the two-dimensional quadratic Hamiltonian, it may be applied to investigate the evolution operators of any Hamiltonian having a dynamical algebra with a large number of elements. We illustrate the method by finding the propagator and the Heisenberg picture position and momentum operators for a two-dimensional charge subject to uniform and constant electro-magnetic fields., Comment: 17 pages, 3 tables