Hardening (metallurgy)

About: Hardening (metallurgy) is a research topic. Over the lifetime, 25584 publications have been published within this topic receiving 376012 citations.

An Evaluation of Recent Developments in Hardening and Flow Rules for Rate-Independent, Nonproportional Cyclic Plasticity

Abstract: The Mroz kinematic hardening rule has previously demonstrated superior capability to correlate cyclically stable nonproportional stress-strain response. In this paper, recently proposed kinematic hardening rules for single and multiple surface cyclic plasticity models are evaluated. Significant improvement over the Mroz rule, without loss of generality, is achieved with a deviatoric stress rate-dominated rule proposed by Tseng and Lee for two surface theory. Recent approaches for correlation of the modulus function and isotropic hardening are discussed. The norm of the Mroz distance vector is found to uniquely correlate the variation of plastic hardening modulus through a cycle; it is necessary to include a measure of instantaneous nonproportionality, however, to properly normalize the modulus function. A new evolution equation is offered to correlate the additional isotropic hardening observed during nonproportional loading, and several contemporary approaches are also considered.

Stress Corrosion Cracking of Stainless Steels and Nickel Alloys in High-Temperature Water

Abstract: Stress corrosion cracking (SCC) studies in stainless steels and nickel alloys reveal that all grades and conditions are susceptible to SCC in high-temperature water, whether deaerated or aerated, high H2 or low, theoretical purity water or buffered/contaminated, lower temperature or higher. However, the kinetics of SCC growth vary enormously with stress intensity, yield strength, sensitization, water chemistry, irradiation, temperature, etc. The role of yield strength is especially important because it changes with surface cold work, bulk cold work, weld shrinkage strain, and irradiation hardening; the role of metallurgical strengthening mechanisms, e.g., nitrogen additions or precipitation hardening, may have a similar effect. SCC growth rate measurements were performed in high-temperature water on unsensitized stainless steels (and Alloy 600 [UNS N06600]) of various grades and compositions. Little effect of grade/heat of stainless steel, martensite content, or H2 fugacity/permeation rate was ob...

An elasto-plastic self-consistent model with hardening based on dislocation density, twinning and de-twinning: Application to strain path changes in HCP metals

Abstract: In this work, we develop a polycrystal mean-field constitutive model based on an elastic–plastic self-consistent (EPSC) framework. In this model, we incorporate recently developed subgrain models for dislocation density evolution with thermally activated slip, twin activation via statistical stress fluctuations, reoriented twin domains within the grain and associated stress relaxation, twin boundary hardening, and de-twinning. The model is applied to a systematic set of strain path change tests on pure beryllium (Be). Under the applied deformation conditions, Be deforms by multiple slip modes and deformation twinning and thereby provides a challenging test for model validation. With a single set of material parameters, determined using the flow-stress vs. strain responses during monotonic testing, the model predicts well the evolution of texture, lattice strains, and twinning. With further analysis, we demonstrate the significant influence of internal residual stresses on (1) the flow stress drop when reloading from one path to another, (2) deformation twin activation, (3) de-twinning during a reversal strain path change, and (4) the formation of additional twin variants during a cross-loading sequence. The model presented here can, in principle, be applied to other metals, deforming by multiple slip and twinning modes under a wide range of temperature, strain rate, and strain path conditions.