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American Society for Testing and Materials

Principles of equal-channel angular pressing as a processing tool for grain refinement

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.

Recent developments in stainless steels

Cumulative fatigue damage and life prediction theories: a survey of the state of the art for homogeneous materials

Dislocation wall and cell structures and long-range internal stresses in deformed metal crystals

Current state and historical progress in experimental and theoretical studies of surface relief appertaining to persistent slip bands (PSBs) and leading to fatigue crack initiation in cyclically deformed metals is presented as a thorough critical overview. A comprehensive inventory of microscopic techniques used for this study is tabulated chronologically with emphasis to their applicability to polycrystals. The most relevant experimental characteristics concerning surface relief evolution, namely the form of extrusions and intrusions in single- and polycrystalline materials, are surveyed. Theoretical models and computational simulations of extrusion and intrusion formation and fatigue crack initiation are critically reviewed. †In 2003, it was 100 years since J.A. Ewing and J.C.W. Humfrey first documented the nature of early surface fatigue damage in Swedish iron in their paper The Fracture of Metals under Repeated Alternations of Stress published in the journal Philosophical Transactions of the Royal Soc...

Extrusions and intrusions in fatigued metals. Part 1. State of the art and history

1 Introduction 2 Stress and Strain in Cyclic Loading Monotonic stress-strain curve Stress-strain relationship in cyclic loading Hysteresis loop Cyclic hardening/softening curves Cyclic stress-strain curve 3 Cyclic Plasticity and Microstructure Metals and simple alloys with fcc structure Metals and single phase alloys with bcc structure Other metals and single phase alloys Multiphase materials 4 Dislocation Mechanisms in Cyclic Plastic Straining Athermal mechanisms in fcc metals Thermally activated cyclic straining Dislocation mechanisms in particle strengthened metals 5 Statistical Description of Cyclic Stress-Strain Response Internal and effective stress in an elementary volume Statistical approach 6 Experimental Investigation of the Dynamics of Cyclic Plastic Straining Stress-dip method Stress and strain relaxation Strain rate changes Analysis of hysteresis loop shape Evaluation of results using individual methods 7 Cyclic Creep Relevant experimental investigations Dislocation arrangements Mechanisms and models 8 Fatigue Crack Initiation Observation of surface relief evolution Models of surface relief evolution Mechanisms of crack initiation Role of grain boundaries Role of inclusions 9 Growth of Fatigue Cracks Fracture mechanics approach to fatigue crack growth Crack growth under small scale yielding General yield fatigue crack growth Short crack growth 10 Fatigue Life of Smooth Bodies Strain controlled cycling Plastic strain controlled cycling Stress controlled cycling Energy criterion Evaluation of fatigue life of a smooth body using the fatigue process model 11 Fatigue Life of Notched Bodies Stress and strain concentration in a notched body Fatigue life evaluation 12 Variable Amplitude Loading Phenomenological description Analysis of load history Sudden changes of strain amplitude Cyclic plasticity in repeated block loading Hypothesis of cumulative damage Fatigue life prediction 13 Effect of Depressed Temperature Cyclic plasticity Fatigue life 14 High Temperature Low Cycle Fatigue Cyclic plasticity at elevated temperatures Fatigue life and its evaluation Damage mechanisms Fatigue life prediction 15 Thermal and Thermomechanical Fatigue The effect of temperature changes under constraint Reversed plasticity and thermal cracking Thermal ratchetting 16 Multiaxial Loading Multiaxial stress and strain Cyclic stress-strain response Fatigue life 17 Computer Controlled Fatigue Testing Role of the digital computer Low cycle fatigue test Crack growth test Variable amplitude test Other tests 18 Characterisation of Low Cycle Fatigue Resistance of Metallic Materials Basic characteristics Review of materials properties References Subject Index

Cyclic Plasticity and Low Cycle Fatigue Life of Metals

Atomic force microscopy of surface relief in individual grains of fatigued 316L austenitic stainless steel

On the role of point defects in fatigue crack initiation

Atomic force microscopy was applied to study the surface relief evolution at emerging persistent slip bands (PSBs) in individual grains of polycrystalline 316L stainless steel cycled with constant plastic strain amplitude. Quantitative data on the changes of the surface topography of persistent slip markings (PSMs) and on the kinetics of extrusion growth during the fatigue life of smooth specimens were obtained. The extrusion height can be assessed by a direct observation of the metal surface and the intrusion depth using the plastic replica technique. The first PSMs appear after the initial hardening (0.1–0.25% of Nf). PSBs can be active in the whole period of fatigue life in grains in which no cracks develop. The initial rapid growth of extrusions is followed by a period of stable linear growth up to the end of the fatigue life. The width of extrusions, corresponding to the thickness of the emerging PSBs quickly stabilizes and remains constant during the whole fatigue life. The experimental results are discussed in terms of recent vacancy models of surface relief evolution.

Jaroslav Polák

Papers

Extrusions and intrusions in fatigued metals. Part 1. State of the art and history

Cyclic Plasticity and Low Cycle Fatigue Life of Metals

Atomic force microscopy of surface relief in individual grains of fatigued 316L austenitic stainless steel

On the role of point defects in fatigue crack initiation

Study of surface relief evolution in fatigued 316L austenitic stainless steel by AFM