Hydrogen-dislocation Interaction Research Articles

An internal friction peak caused by hydrogen in maraging steel

Internal friction in hydrogen-charged iron and steel has so far been studied by a large number of investigators. For pure iron, a well-defined peak of internal friction has been observed under the cold-worked and hydrogen-charged conditions. This is called the hydrogen cold-work peak, or the Snoek-Koester relaxation, which originates from the hydrogen-dislocation interaction. In the present study, a high-strength maraging steel (Fe-18Ni-9Co-5Mo) was chosen as another high-alloy steel which is known to be very susceptible to hydrogen embrittlement. The purpose of this paper is to show a new internal friction peak caused by hydrogen in the maraging steel and to compare it with those found in stainless steels which have so far been studied as typical engineering high-alloy materials.

Application of finite element methods (FEM) to compaction of metal powders: B.B. Hwang, S. Kobayashi, (Univ of California, California, USA), Int. J. Machine Tools Manufacture, Vol 31, No 1, 1991, 123–137

The hydrogen embrittlement (HE) of Al-2.30 Li-1.24 Cu-0.80 Mg-0.12 Zr and Al-1.90 Li-1.80 Cu-1 Mg-0.09 Zr alloys in different artificial aging tempers and after retrogression and reaging (RRA) treatments has been investigated by tensile testing hydrogen precharged specimens. The influence of RRA and hydrogen charging on the dislocation structure was studied by TEM. The under-aged temper was the most susceptible while the peak-aged temper was the most resistant to HE. The RRA treatment improved the HE resistance of all the tempers. This has been attributed to the reduction in dislocation density upon retrogression and reaging. The alloy with the lower Li content exhibited improved HE resistance. Flat fractographic features near the surface of the hydrogen charged specimen have been correlated to the depth of hydrogen penetration. The formation of LiAlH4 and LiH in hydrogen charged AlLi alloys has been confirmed by X-ray diffraction studies. The hydrogen-dislocation interaction and hydride cracking mechanisms of HE have been addressed.

The mechanism of a hydrogen-dislocation interaction in b.c.c. metals: Embrittlement and dislocation motion

In this paper the interaction between a Peierls-Nabarro edge dislocation and a hydrogen ion in the core of the dislocation is characterized. The model assumes the formation of a chemical bond between the metal atoms at the dislocation line and hydrogen. The center of charge of this bond is shifted towards the hydrogen. The compressive strain caused by the presence of a hydrogen ion (with a Pauling radius of 0.153 nm) at the dislocation core is shown to be related to the hydrogen-edge dislocation interaction energy in niobium, iron, vanadium and tantalum. The agreement between our calculations and the results from hydrogen-related internal friction is excellent. This supports the idea of a continuous injection of dislocations to a growing crack tip. A discussion of the embrittlement phenomena, the dislocation solute saturation and the chemisorption kinetics of hydrogen in b.c.c. iron is also presented.

On the interaction hydrogen-dislocations in palladium

The influence of hydrogen, introduced by cathodization, on the dissipation of elastic energy in bars of plasticaly deformed palladium, vibrating flexurally, has been investigated in the temperature interval (80÷300) K, for frequencies in the kilocycle range. It has been found that the dislocations produced by plastic deformation give rise to two relaxation effects, having different properties. One of these effects is of intrinsic type, takes place when the material is deformed but not cathodized and is probably due to straight dislocation segments lying along Peierls valleys. The other effect appears to be due to the interaction of hydrogen with dislocation segments having their extremes anchored in different Peierls valleys and containing, therefore, geometrical kinks. The results are compared with those obtained in other f.c.c. metals (nickel, copper) and with the predictions of the available theories on hydrogen-dislocation interaction.

Elastic energy dissipation in the palladium-silver-hydrogen(deuterium) system. I. Hydrogen-dislocation interaction effects

Measurements are reported of the elastic energy dissipation coefficient, Q-1, following absorption of hydrogen into a series of palladium-silver alloys, which initially had been in both pre-annealed and mechanically deformed states. The measurements have enabled assessments to be made of the extents to which peaks in plots of Q-1 against temperature over the range 85-300K can be attributed either to the hydrogen-dislocation interaction or to relaxation effects associated with reordering of hydrogen interstitials and vacant interstitial sites in the bulk lattice.

Elastic energy dissipation effects in the palladiumhydrogen system

We have carried out systematic studies, over a wide range of both increasing and decreasing hydrogen contents n in the Pd- H ( PdH n ) system, of elastic energy dissipation (internal friction) peaks associated with relaxation processes arising from (1) a Zener type of effect due to stress-induced rearrangements of interstitial hydrogen and vacant interstitial sites (H (1) peak) and (2) a hydrogen-dislocation interaction effect related to the dragging of hydrogen interstitials by moving dislocations (H (2)) peak). Over the ( α + β)-phase range of n, the dependence of the relaxation strength of the H (1) peak on n has been shown to be dependent on the distribution of β-phase regions. Asymmetries of the H (1) peak in purely β-phase regions and the dependence of its relaxation strength on n have been examined and are discussed in terms of a Zener relaxation effect. The H (2) peak has not been found to be evident in β-phase regions. The height Q −1 M of the H (2) peak and its position T M on the temperature scale in α- and( α + β)-phase regions have been examined under conditions in which associated dislocation networks were introduced both by mechanical deformation and in the course of ααβ phase transitions.

The hydrogen-dislocation interaction in 17% chromium steel

The hydrogen-dislocation interaction in 17% chromium steel

Hydrogen-dislocation Interaction and Its Parallelism with Hydrogen Embrittlement

Hydrogen-dislocation Interaction and Its Parallelism with Hydrogen Embrittlement

Embrittlement kinetics of N 80 steel in H2S environment

The kinetics of hydrogen embrittlement of an N 80 steel have been studied in a Na2S-CH3COOH solution. Determination of hydrogen content, metal density and embrittlement degree, together with acoustic-emission measurements have shown that the hydrogen distribution with-in the metal lattice is time-dependent and strongly influenced by non-metallic inclusions. The inclusions cause local stress intensification, favoring hydrogen collection in the lattice around them. Fracturing of charged specimens at different times evidences a mechanism of crack inactivation. An explanation of crack inactivation in terms of plastic deformation around inclusions due to hydrogen-dislocation interaction is suggested.

A study of dislocation-hydrogen interaction in α-titanium via internal friction measurements

A hydrogen-dislocation interaction in α-titanium was studied via internal friction measurements of a damping peak in the temperature range 200°–500°K. The peak centers around 390°K at 10 MHz. The activation energy and pre-exponential factor are 6,400 cal/mole (= 0.28 eV) and 4 × 10 10 cycles/ sec, respectively. Both room temperature plastic deformation and the presence of hydrogen are required to generate this peak. The relaxation strength of the peak is proportional to the square of the hydrogen concentration at very low concentrations, and reaches a plateau at 8 ppm total hydrogen concentration. The peak relaxation strength diminishes with time at elevated temperatures, and the activation energy associated with this process was determined to be 11.5 ± 0.9 kcal/ mole. This energy is comparable with the diffusion energy of hydrogen in α-titanium. The mechanism of this peak is proposed to be due to the interaction of hydrogen di-interstitials in α-titanium solid solution with dislocation loops in a manner similar to that suggested earlier by Hasiguti to depict point defect-dislocation interactions. The activation energy required is that needed for dislocation loops to detrap from hydrogen di-interstitials, that is, the binding energy between dislocation loops and hydrogen di-interstitials. It is proposed that the origin of this binding energy is electrical in nature.

Further comments on the hydrogen dislocation interaction in iron

Further comments on the hydrogen dislocation interaction in iron

Hydrogen-dislocation interaction in iron

Hydrogen-dislocation interaction in iron