<i>Fundamentals of Creep and Creep-Rupture in Metals</i>

Garofalo, F.; Butrymowicz, Daniel B.

doi:10.1063/1.3048224

Cited by 435 publications

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“…This value was almost same as the activation energy obtained by hot deformation studies in various wrought HSLA steels and austenitic stainless steel, 13,24) although it is higher than activation energy of self diffusion of iron in austenite (210-310 kJ/mol). 25) These results indicate activation energy for dynamic restoration process in austenite may be influenced a very little by alloying elements, their content or micro segregation. In the previous study using as cast HSLA steels, S-S curves and flow stress were evidently different between the specimens prepared from as cast steel and hot rolled plates, in particular, in the steels containing a small amount of Ti around 0.02 %.…”

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confidence: 83%

Effects of Dynamic Recrystallization on .GAMMA. Grain Refinement and Improvement of Micro Segregation of As Cast Austenite in 9% Ni Steel

et al. 2005

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Effects of dynamic recrystallization on g grain refinement and improvement in micro segregation of elements such as Ni and Mn of as cast austenite in 9 % Ni steel were investigated by two kinds of experimental methods. The first one was a hot compression test using the specimens prepared from the strand cast slab and the hot rolled plate of 9 % Ni steel, and the other was a hot tensile straining test in the austenitic region after levitation melting and solidification. In the hot compression test, variations in onset strain and flow stress of steady state flow of dynamic recrystallization with hot deformation conditions were investigated. The onset strain was found to decrease below 0.25 at the temperatures above 1 523 K and the strain rate below 1ϫ10 Ϫ2 s Ϫ1. The activation energy value obtained from steady state flow stress was 421 kJ/mol. Dynamically recrystallized g grain size in as cast austenite of this steel was controlled simply by Z value with no dependence on the initial g grain size. This beneficial feature of dynamic recrystallization was confirmed by the experiment of tensile straining in austenite formed after levitation melting and solidification, where extremely coarse initial g grain size of around 1.9 mm was markedly refined down to 140 mm by straining such a small strain as 0.40. Micro segregation ratio of Ni and Mn in the strand cast 9 % Ni steel examined by EPMA analysis was 1.20 and 1.36, respectively. These values were found to decrease continuously with reduction in strain rate in hot deformation of austenite. That is, dynamic recrystallization in austenite taken place at lower strain rate deformation is much more effective for homogenization of segregated elements compared with high strain rate deformation.

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confidence: 83%

Effects of Dynamic Recrystallization on .GAMMA. Grain Refinement and Improvement of Micro Segregation of As Cast Austenite in 9% Ni Steel

et al. 2005

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“…The activation energies calculated by this procedure for the Al-14.6 %Zn alloy from the entire series of dilatometric experiments in a temperature range of 373 K to 823 K are given in Table 1. Note that the proposed procedure has some advantages over the currently used procedure for the determination of the activation energies on the basis of the theory of absolute reaction rates (TARR) [8]. The new method rests on the assumption about the constancy of the pre-exponential factor in a substantially smaller temperature interval (2 K to 5 K) than that used in TARR and is based on a substantially larger volume of experimental measurements (up to a thousand at each stage).…”

Section: Resultsmentioning

confidence: 99%

Structural Mechanisms of Dilatometric Processes

2013

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Temperature actions on metals and alloys usually stimulate the development of irreversible processes of structural evolution. Dilatometric hysteresis can be considered as the total effect of such processes. The elementary mechanisms affecting the sample size upon heating are known to be the thermal expansion of materials, the phase and structural transformations, the ductile flow under its own weight, and the creep stimulated by internal stresses. Each of these mechanisms has specific features, which are unavoidably reflected by the shape of the dilatometric curves in the corresponding temperature ranges. The thermal activation parameters of the mechanisms controlling the kinetics of the change in structural parameters and the development of the corresponding size effects have been determined by photometric analysis of structural images and directly from the dilatometric curves, and the results are discussed in this paper.

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“…These constitutive relations can in general be written as strain-stress relationships (Garofalo 1965;Conway and Flagella 1971;Bressers 1981). For example, Hallvard and Asbjorn (1990) fit the experimental data of Nedreberg (1990) for A6063, an AlMgSi alloy, by using predefined functions (power law) for the stress, strain, and hardening parameters.…”

Section: Modeling Of Alloy Deformation (Shell-alloy Interaction)mentioning

confidence: 99%

Predicting Pattern Tooling and Casting Dimensions for Investment Casting - Phase II

Sabau¹

2005

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We would like to thank M. Argueso & Co., Inc., for providing the wax for this study; T. Wolf, P. A. Silverstein, W. R. Fricker, and I. Al-Rabadi of Argueso for assistance with the wax injection experiments; G. Rowe of Abatech, Inc., for obtaining the viscoelastic relaxation spectrum from rheometry data; and T. A. Parham and C. M. Smith for assistance with pressure transducer thermocouples.Thanks also go to Srinath Viswanathan of ORNL, with whom we collaborated on past project tasks and who supervised the work on Sections 1, 2.1, and 2.2. We thank J. Snow, D. Scott, and B. Sneider of Minco, Inc., for shell investment and for embedding thermocouples within the shell; E. Hatfield for casting assistance; Z. Wu, a University of Tennessee graduate student, for obtaining the shrinkage factors from measured dimensions; J. Kovatch and R. Abramczyk of Precision Metalsmiths, Inc. (PMI), for conducting casting experiments; Allen Bransford and Mike Payne, Precision Castings of Tennessee, Inc., for providing access to their foundry; B. Schrey, of Schrey & Sons Mold Co., for providing the sprue tooling; and Jim Gardner, J.E.M. Manufacturing, for casting design and providing wax patterns for the sprue.Oak Ridge National Laboratory is operated by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. We wish to thank Peter Angelini, ORNL, for project guidance and review.

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Fundamentals of Creep and Creep-Rupture in Metals

Cited by 435 publications

References 0 publications

Effects of Dynamic Recrystallization on .GAMMA. Grain Refinement and Improvement of Micro Segregation of As Cast Austenite in 9% Ni Steel

Effects of Dynamic Recrystallization on .GAMMA. Grain Refinement and Improvement of Micro Segregation of As Cast Austenite in 9% Ni Steel

Structural Mechanisms of Dilatometric Processes

Predicting Pattern Tooling and Casting Dimensions for Investment Casting - Phase II

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