Journal ArticleDOI
HVEM studies of the effects of hydrogen on the deformation and fracture of AISI type 316 austenitic stainless steel
TLDR
In this paper, hydrogen embrittlement in AISI type 316 austenitic stainless steel has been investigated by in situ straining in a highvoltage electron microscope (HVEM) equipped with an environmental cell.Abstract:
The mechanisms of hydrogen embrittlement in AISI type 316 austenitic stainless steel have been investigated by in situ straining in a high-voltage electron microscope (HVEM) equipped with an environmental cell. Hydrogen effects on strain-induced phase transformations, the generation rate and velocity of dislocation, and crack propagation rates were studied. The salient features of the fracture were similar for cracks propagating in vacuum and in hydrogen gas. In each case, e and α′ martensite formed at the crack; the e phase extended ahead of the crack while the α′ phase was restricted to high stress regions near the crack tip. The principal effect of hydrogen was to decrease the stress required for dislocation motion, for phase transformation of the austenite, and for crack propagation.read more
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Journal ArticleDOI
Recent developments in stainless steels
Abstract: This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.
Journal ArticleDOI
Hydrogen-enhanced localized plasticity—a mechanism for hydrogen-related fracture
TL;DR: In this article, a theory of hydrogen shielding of the interaction of dislocations with elastic stress centres is outlined, which can account for the observed hydrogen-enhanced dislocation mobility.
Journal ArticleDOI
The effect of hydrogen on dislocation dynamics
TL;DR: In this paper, the authors performed deformation studies in situ in a transmission electron microscope equipped with an environmental cell to elucidate the mechanisms of hydrogen embrittlement and found that solute hydrogen can increase the velocity of dislocations, increase the crack propagation rate, decrease stacking-fault energy of 310s stainless steel and increase the propensity for edge character dislocation.
Journal ArticleDOI
Hydrogen Embrittlement Understood
Ian M. Robertson,Ian M. Robertson,Petros Athanasios Sofronis,Petros Athanasios Sofronis,Akihide Nagao,May L. Martin,Shuai Wang,Shuai Wang,D. W. Gross,Kelly E. Nygren +9 more
TL;DR: The connection between hydrogen-enhanced plasticity and the hydrogen-induced fracture mechanism and pathway is established through examination of the evolved microstructural state immediately beneath fracture surfaces including voids, quasi-cleavage, and intergranular surfaces as discussed by the authors.
Journal ArticleDOI
Hydrogen effects on the interaction between dislocations
TL;DR: The effect of hydrogen on the interaction between dislocations and other elastic centers in high-purity aluminum and stainless steel has been directly observed during deformation experiments in situ in an environmental cell transmission electron microscope as discussed by the authors.
References
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Journal ArticleDOI
A new model for hydrogen-assisted cracking (hydrogen “embrittlement”)
TL;DR: A new model for hydrogen-assisted cracking is presented in this article, which explains the observations of decreasing microscopic plasticity and changes of fracture modes with decreasing stress intensities at crack tips during stress-corrosion cracking and HAC of quenched-and tempered steels.
Journal ArticleDOI
Equilibrium aspects of hydrogen-induced cracking of steels
R.A. Oriani,P.H. Josephic +1 more
TL;DR: In this paper, the threshold pressures, p ∗, of hydrogen and of deuterium gases necessary to cause crack propagation in AISI 4340 steel of 250 ksi yield strength, were determined as functions of plane-strain stress intensity factor K at room temperature.
Journal ArticleDOI
Hydrogen embrittlement of metals
TL;DR: The deleterious effects of hydrogen on the tensile properties of metals are caused by the association and movement of hydrogen with dislocations as discussed by the authors, and hydrogen-dislocation interactions modify plastic deformation processes by stabilizing microcracks, by changing the work hardening rate, and by solid solution hardening.
Journal ArticleDOI
Hydrogen transport by dislocations
TL;DR: In this article, a kinetic model for the transport of hydrogen, as Cottrell atmospheres on dislocation, at a rate appreciably in excess of that for lattice diffusion is presented.
Journal ArticleDOI
An HVEM study of hydrogen effects on the deformation and fracture of nickel
Ian M. Robertson,H.K. Birnbaum +1 more
TL;DR: In this article, the authors investigated the mechanisms of hydrogen "embrittlement" of nickel by performing in situ straining experiments in a highvoltage electron microscope equipped with an environmental cell.
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