scholarly journals Optimization of Interfacial Energy for Langer-Schwartz Based Precipitation Simulations

2021 ◽  
Author(s):  
Conner Sarich ◽  
Adam Hope ◽  
Jim Rule
Keyword(s):  
Experimental Data ◽  
Interfacial Energy ◽  
Volume Fraction ◽  
Published Data ◽  
Low Alloy Steels ◽  
Interfacial Energies ◽  
Nucleation Sites ◽  
Alloy Steels ◽  
Thermal Histories ◽  
Al 2024

Abstract Precipitation kinetics were investigated in select Fe, Ni, and Al alloys using a CALPHAD based precipitation model based on Langer-Schwartz theory. Thermodynamic and kinetic data are taken from commercially available CALPHAD software, but reliable interfacial energy data for precipitates needed for the calculations is often lacking. While models exist to approximate these interfacial energies, this study has focused on deriving more reliable estimates by comparison with experimental data. By performing simulations with thermal histories, nucleation sites, and precipitate morphologies that closely replicate experimental data found in literature, the interfacial energies were optimized until volume fraction and mean radius values closely matched the published data. Using this technique, interfacial energy values have been determined for carbides in Grade 22 low alloy steels, delta phase in Ni 625 and 718, SPhase in Al 2024, and Q’ and β’’ in Al 6111, and can be used for future predictive precipitation simulations.

On the Materials Requirements for a Solar Solid-Expansion Machine

2000 ◽  
Vol 122 (3) ◽  
pp. 154-157
Author(s):  
B. J. Brinkworth
Keyword(s):  
Figure Of Merit ◽  
High Strength ◽  
Solar Thermal ◽  
Low Alloy Steels ◽  
Expansion Engine ◽  
Alloy Steels ◽  
Thermal Histories ◽  
Engineering Alloys ◽  
Selection Of

An outline is given of the mechanical and thermal histories of the working substance for a generic stand-alone solar thermal solid-expansion engine. A Figure-of-merit for the selection of materials is devised and evaluated, showing that high-strength engineering alloys figure best for this duty, with the carbon and low-alloy steels a practical choice. [S0199-6231(00)00403-2]

Formation of Ultrafine Grained Ferrite by Warm Deformation of Tempered Lath Martensite in Low Alloy Steels

2007 ◽  
Vol 558-559 ◽  
pp. 557-562 ◽  
Author(s):  
Behrang Poorganji ◽  
Takuto Yamaguchi ◽  
Tadashi Maki ◽  
G. Miyamoto ◽  
Tadashi Furuhara
Keyword(s):  
Grain Size ◽  
Carbon Content ◽  
Volume Fraction ◽  
Boundary Migration ◽  
Lath Martensite ◽  
Second Phase ◽  
Low Alloy Steels ◽  
Warm Deformation ◽  
Alloy Steels ◽  
Block Width

Microstructure change during warm deformation of tempered lath martensite in Fe-2mass%Mn-C alloys with different carbon contents in the range between 0.1 and 0.8mass%C was investigated. Specimens of the alloys after being quenched and tempered at 923K for 0.3ks were compressed by 50% with a strain rate varying from 10-3 to 10-4s-1 at 923K. EBSD analysis of the deformed microstructures has revealed that fine equiaxed ferrite (α) grains surrounded by high-angle boundaries are formed by dynamic recrystallization (DRX). As carbon content increases, the DRX α grain size decreases. This could be attributed to the change in volume fraction of the cementite (θ) phase as boundary dragging particles. The sub-micron θ particles can suppress the coarsening of the DRX α grains by exerting a pinning effect on grain boundary migration. Furthermore, the fraction of recrystallized region increases by increasing carbon content, presumably due to a decrease in the martensite block width as an initial α grain size and a larger volume fraction of hard second phase (θ) particles. Both of these should increase inhomogeneous plastic deformation which promotes the recrystallization. It seems that continuous DRX is responsible for the formation of ultrafine α grains in the tempered lath martensite.

Impurities, segregation and creep embrittlement

1980 ◽  
Vol 295 (1413) ◽  
pp. 265-278 ◽  
Keyword(s):  
Surface Segregation ◽  
Rupture Life ◽  
Boundary Segregation ◽  
Impurity Content ◽  
Stress Relief ◽  
Published Data ◽  
Low Alloy Steels ◽  
Creep Ductility ◽  
Internal Surfaces ◽  
Alloy Steels

Reported studies of creep embrittlement in low alloy steels at 550 °C and of stress relief cracking at 700 °C show conflicting evidence for the importance of residual impurities. Calculations of the relative effects of impurities, through segregation to grain boundaries and also to the internal surfaces of cavities, show that rupture life and ductility can be affected. Auger electron spectroscopic measurements of these segregations in commercial ½CrMoV steels give the relative importance for all active elements. For stress relief cracking, the equilibrium surface segregation results agree with cracking measurements and allow extension to all important elements. Analysis of published data shows that, in practice, impurities are as important as microstructure in causing embrittlement, the most important impurities being, equally, tin, copper and arsenic. A similar analysis for creep shows that impurities are more important than microstructure with copper dominant and phosphorus and tin also detrimental. Here, the creep ductility falls but rupture life increases with impurity content, consistent with a model involving grain boundary segregation. The stress relief cracking and creep embrittlement are both sensitive to impurities but, involving different segregations, are dominated by different elements.

In Situ Neutron Diffraction during Thermo-Mechanically Controlled Process in Low Alloy Steels

2006 ◽  
Vol 118 ◽  
pp. 419-424
Author(s):  
M.S. Koo ◽  
Ping Guang Xu ◽  
J.H. Li ◽  
Yo Tomota ◽  
O. Muransky ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Volume Fraction ◽  
Structural Evolution ◽  
Low Alloy Steels ◽  
Controlled Processing ◽  
Ferrite Transformation ◽  
Alloy Steels ◽  
Time Division ◽  
In Situ Neutron Diffraction

A challenge was made to examine the micro-structural evolution during thermomechanically controlled processing (TMCP) by in situ neutron diffraction. Since the neutron beam is too weak to achieve a time-division measurement to follow a rapid transformation in alow carbon steel, 2%Mn was added to make the austenite to ferrite transformation slower. Round bar specimens were heated up to 900°C with an electrical resistance method, then cooled down to 700°C, and compressed by 25% followed by step-by-step cooling. During the step-by-step cooling, neutron diffraction profiles were obtained and the volume fraction of ferrite, phase stresses and FWHM were analyzed. Using a similar TMCP simulator, specimens were quenched into water at several stages of the heat schedule to freeze the corresponding microstructures, which were observed with OM and SEM. As results, the ferrite volume fraction determined by neutron diffraction on cooling agrees well with that by microscopy. It is found that the austenite deformation and/or Nb addition accelerate the ferrite transformation to result in finer grain size.

scholarly journals Microstructure, hardness and interfacial energy in Co-9Al-10W-xNi (x=15, 25, 35 at. %) alloys during aging

2017 ◽  
Vol 53 (3) ◽  
pp. 303-308 ◽  
Author(s):  
C. Che ◽  
S. Yang ◽  
M. Wei ◽  
L. Zhang ◽  
Q. Li ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Interfacial Energy ◽  
Aging Temperature ◽  
Volume Fraction ◽  
Ni Alloys ◽  
Interfacial Energies ◽  
Ni Content ◽  
Coarsening Kinetics ◽  
The Relationship ◽  
Kinetics Of

In the present paper, three Co-Al-W-Ni alloys (i.e., Co-9Al-10W-xNi with x=15, 25, 35 at. %) and their heat treatment mechanisms were carefully designed on the basis of the available phase equilibrium information. The temporal evolution of the microstructure and hardness in the Co-9Al-10W-xNi (x=15, 25, 35) alloys during aging process was measured, from which the effect of additional Ni contents, aging temperature and time on microstructure and hardness in the three Co-Al- W-Ni alloys was analyzed. Considering that the alloy compositions and heat treatment are not directly related with the hardness, the relationship between hardness and microstructure was then linked. It was found that the hardness of Co-based superalloys increases as the volume fraction of ?' precipitates increases, while decreases with the increase of the radius and interval of ?' precipitates. Moreover, the interfacial energy of ?/?' interface was also evaluated on the basis of the coarsening kinetics of ?' precipitates and the Philippe-Voorhees model in combination with the thermodynamic and atomic mobility databases. The results indicate that the interfacial energies of ?/?' interface reduce as the increase of additional Ni content and aging temperature.

scholarly journals Investigation of Hydrogen Embrittlement Susceptibility and Fracture Toughness Drop after in situ Hydrogen Cathodic Charging for an X65 Pipeline Steel

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 430 ◽  
Author(s):  
Helen Kyriakopoulou ◽  
Panagiotis Karmiris-Obratański ◽  
Athanasios Tazedakis ◽  
Nikoalos Daniolos ◽  
Efthymios Dourdounis ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
High Strength ◽  
Electrolytic Cell ◽  
Low Alloy Steels ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Alloy Steels

The present research focuses on the investigation of an in situ hydrogen charging effect during Crack Tip Opening Displacement testing (CTOD) on the fracture toughness properties of X65 pipeline steel. This grade of steel belongs to the broader category of High Strength Low Alloy Steels (HSLA), and its microstructure consists of equiaxed ferritic and bainitic grains with a low volume fraction of degenerated pearlite islands. The studied X65 steel specimens were extracted from pipes with 19.15 mm wall thickness. The fracture toughness parameters were determined after imposing the fatigue pre-cracked specimens on air, on a specific electrolytic cell under a slow strain rate bending loading (according to ASTM G147-98, BS7448, and ISO12135 standards). Concerning the results of this study, in the first phase the hydrogen cations’ penetration depth, the diffusion coefficient of molecular and atomic hydrogen, and the surficial density of blisters were determined. Next, the characteristic parameters related to fracture toughness (such as J, KQ, CTODel, CTODpl) were calculated by the aid of the Force-Crack Mouth Open Displacement curves and the relevant analytical equations.

The influence of nitrogen on the oxidation resistance of low alloy steels

1980 ◽  
Vol 295 (1413) ◽  
pp. 336-336
Keyword(s):  
Surface Layer ◽  
Mild Steel ◽  
Oxidation Resistance ◽  
Nitrided Layer ◽  
Low Alloy Steels ◽  
Fine Grain ◽  
Nucleation Sites ◽  
Alloy Steels ◽  
Nitrided Surface ◽  
Cyclic Changes

Experiments in simulated boiler flue gas have shown that the oxidation resistance of mild steel is increased by up to two orders of magnitude by a surface nitriding treatment. Oxidation resistance was determined under isothermal conditions and during cyclic changes of temperature and oxygen potential. The oxide scale has a fine grain size, is extremely adherent and is therefore protective. A nitrided surface layer is produced by gas-metal equilibration with NH 3 : H 2 gas mixtures under conditions to form austenite (y) at nitriding temperature. On cooling to room temperature, martensite (a') is formed with retained austenite, the relative proportions of which depend on cooling rate. During oxidation at 420 °C, martensite and austenite in the immediate surface layer temper within a few minutes to form ferrite (a) containing a fine dispersion of y'-Fe 4 N platelets ca . 50 nm in diameter. X-ray analysis at increasing depth from the surface of nitrided mild steel shows that tempering of the a' + y structure to a + y'-Fe 4 N is accelerated at the free surface of the alloy relative to the remainder of the nitrided layer, and results in formation of incoherent nitride precipitates on the surface. The nitride particles act as nucleation sites for oxide formation, and electron microscopy shows that the oxide nuclei are of the same order of size as the nitride particles.

Microstructure-Impact Toughness Relationships in Quenched and Tempered Low Carbon Low Alloy Steels

2021 ◽  
Vol 887 ◽  
pp. 216-221
Author(s):  
M. Kantor ◽  
K. Vorkachev ◽  
K. Solntsev
Keyword(s):  
Impact Toughness ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
High Volume ◽  
Low Alloy Steels ◽  
Low Carbon ◽  
Cooling Conditions ◽  
Alloy Steels ◽  
Ebsd Technique ◽  
Quenching And Tempering

The quantitative microstructure - impact toughness relationships in two batches of the same steel grade subjected to quenching and tempering (Q&T) have been established via characterization using EBSD technique and FIB visualization. The EBSD-based criterion for separation of structural constituents in microstructure of Q&T low carbon low alloy steels is proposed. Impact toughness differences between two steel batches subjected to nominally identical Q&T are caused by the changes in the volume fraction of structural constituents caused by various cooling conditions at quenching stage. High volume fraction of bainite containing more distorted bainitic ferrite and the highest amount of brittle cementite precipitates leads to the increase in strength and to the decrease in impact toughness.

Analysis of variant selection in friction-stir-processed high-strength low-alloy steels

2013 ◽  
Vol 46 (3) ◽  
pp. 716-725 ◽  
Author(s):  
Majid Abbasi ◽  
Tracy W. Nelson ◽  
Carl D. Sorensen
Keyword(s):  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Low Alloy Steels ◽  
Variant Selection ◽  
Dimensional Approach ◽  
Friction Stir ◽  
Interfacial Energies ◽  
Austenite Grain ◽  
Alloy Steels ◽  
Backscatter Diffraction

Variant selection in friction-stir-welded high-strength low-alloy steels has been studied using the electron backscatter diffraction and prior austenite (PA) reconstruction techniques described in previous papers. A hypothesis for variant selection has been proposed based on grain-boundary interfacial energy and misorientation. This study focuses on austenite 〈111〉 boundaries with a two-dimensional approach. Results indicate that variant selection is strongly dependent on misorientation. Certain PA misorientations produce combinations of variants that minimize the interfacial energies between a ferrite nucleus and a neighboring austenite grain, and between adjoining ferrite nuclei along the boundary between two PA grains. PA grains that exhibit a 60° 〈111〉 misorientation between them satisfy both these conditions for a combination of variants. These PA boundaries exhibit strong variant selection. As a result, the density of these boundary types influences the overall variant selection. Additionally, variant selection is more prevalent in small PA grains (<150 µm), which is probably a result of limited intragranular nucleation. Nearly all variants are present in larger PA grains.

Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels

1983 ◽  
Vol 41 ◽  
pp. 220-221
Author(s):  
L.J. Chen ◽  
H.C. Cheng ◽  
J.R. Gong ◽  
J.G. Yang
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Automobile Industry ◽  
High Strength ◽  
Weight Percent ◽  
Low Alloy Steels ◽  
Dual Phase ◽  
Resource Requirement ◽  
Alloy Steels ◽  
Potential Weight

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).

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