scholarly journals Reconstruction of Parent Austenite Grain Structure Based on Crystal Orientation Map of Bainite with and without Ausforming

2011 ◽  
Vol 51 (7) ◽  
pp. 1174-1178 ◽  
Author(s):  
Goro Miyamoto ◽  
Naomichi Iwata ◽  
Naoki Takayama ◽  
Tadashi Furuhara
Keyword(s):  
Crystal Orientation ◽  
Grain Structure ◽  
Austenite Grain ◽  
Orientation Map ◽  
Parent Austenite

scholarly journals On the Formation of Micro-Shrinkage Porosities in Ductile Iron Cast Components

Metals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 551 ◽  
Author(s):  
Ehsan Ghassemali ◽  
Anders Jarfors ◽  
Attila Diószegi
Keyword(s):  
Ductile Iron ◽  
Electron Backscatter Diffraction ◽  
Pressure Change ◽  
Grain Structure ◽  
Absolute Pressure ◽  
Dendrite Fragmentation ◽  
Austenite Grain ◽  
Backscatter Diffraction ◽  
Parent Austenite ◽  
Ebsd Method

A combination of direct austempering after solidification (DAAS) treatment and electron backscatter diffraction (EBSD) method was used to study the formation of micro-shrinkage porosities in ductile iron. Analyzing the aus-ferritic microstructure revealed that most of micro-shrinkage porosities are formed at the retained austenite grain boundaries. There was no obvious correlation between the ferrite grains or graphite nodules and micro-shrinkage porosities. Due to the absolute pressure change at the (purely) shrinkage porosities, the dendrite fragmentation rate during the DAAS process would be altered locally, which caused a relatively finer parent-austenite grain structure near such porosities.

scholarly journals Precipitation Criterion for Inhibiting Austenite Grain Coarsening during Carburization of Al-Containing 20Cr Gear Steels

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 504
Author(s):  
Huasong Liu ◽  
Yannan Dong ◽  
Hongguang Zheng ◽  
Xiangchun Liu ◽  
Peng Lan ◽  
...  
Keyword(s):  
Grain Growth ◽  
Abnormal Grain Growth ◽  
Grain Structure ◽  
Pinning Force ◽  
Grain Coarsening ◽  
Zener Pinning ◽  
Austenite Grain ◽  
Composition Optimization ◽  
Gear Steels ◽  
Grain Growth Behavior

AlN precipitates are frequently adopted to pin the austenite grain boundaries for the high-temperature carburization of special gear steels. For these steels, the grain coarsening criterion in the carburizing process is required when encountering the composition optimization for the crack-sensitive steels. In this work, the quantitative influence of the Al and N content on the grain size after carburization is studied through pseudocarburizing experiments based on 20Cr steel. According to the grain structure feature and the kinetic theory, the abnormal grain growth is demonstrated as the mode of austenite grain coarsening in carburization. The AlN precipitate, which provides the dominant pinning force, is ripened in this process and the particle size can be estimated by the Lifshitz−Slyosov−Wagner theory. Both the mass fraction and the pinning strength of AlN precipitate show significant influence on the grain growth behavior with the critical values indicating the grain coarsening. These criteria correspond to the conditions of abnormal grain growth when bearing the Zener pinning, which has been analyzed by the multiple phase-field simulation. Accordingly, the models to predict the austenite grain coarsening in carburization were constructed. The prediction is validated by the additional experiments, resulting in accuracies of 92% and 75% for the two models, respectively. Finally, one of the models is applied to optimize the Al and N contents of commercial steel.

Back calculation of parent austenite orientation using a clustering approach

2013 ◽  
Vol 46 (1) ◽  
pp. 210-215 ◽  
Author(s):  
V. Tari ◽  
A. D. Rollett ◽  
H. Beladi
Keyword(s):  
Face Centered Cubic ◽  
Orientation Relationships ◽  
New Approach ◽  
Austenite Grain ◽  
Parent Orientation ◽  
Back Calculation ◽  
Clustering Approach ◽  
Face Centered ◽  
Parent Austenite ◽  
Good Agreement

A new approach is presented for calculating the parent orientation from sets of variants of orientations produced by phase transformation. The parent austenite orientation is determined using the orientations of bainite variants that transformed from a single parent austenite grain. In this approach, the five known orientation relationships are used to back transform each observed bainite variant to all their potential face-centered-cubic (f.c.c.) parent orientations. A set of potential f.c.c. orientations has one representative from each bainite variant, and each set is assembled on the basis of minimum mutual misorientation. The set of back-transformed orientations with the minimum summation of mutual misorientation angle (SMMA) is selected as the most probable parent (austenite) orientation. The availability of multiple sets permits a confidence index to be calculated from the best and next best fits to a parent orientation. The results show good agreement between the measured parent austenite orientation and the calculated parent orientation having minimum SMMA.

Analysis of Recrystallization Behavior of Hot-Deformed Austenite Reconstructed from EBSD Orientation Maps of Lath Martensite

2016 ◽  
Vol 879 ◽  
pp. 2389-2394
Author(s):  
Manabu Kubota ◽  
Kohsaku Ushioda ◽  
Goro Miyamoto ◽  
Tadashi Furuhara
Keyword(s):  
Hot Deformation ◽  
Lath Martensite ◽  
New Method ◽  
Reconstruction Method ◽  
Low Alloy Steels ◽  
Recrystallization Behavior ◽  
Compression Direction ◽  
Orientation Map ◽  
Alloy Steels ◽  
Parent Austenite

The recrystallization behavior of hot-deformed austenite of 0.55% C low alloy steels at 900, 850 and 800°C was investigated by a conventional double-hit compression test and a new method which reconstructs the parent austenite orientation map from an EBSD (electron backscattering diffraction) orientation map of daughter lath martensite. The new method can clearly reconstruct the parent austenite structure at high temperature from the daughter lath martensite structure and we can obtain the information on crystal orientation of the work-hardened austenite. It was revealed that recrystallization of austenite at 800 °C is significantly retarded by the addition of 0.1% V. The strong texture of <110> parallel to the compression direction develops just after the hot-deformation, but this texture becomes weaker as the recrystallization progresses. By applying the reconstruction method, it becomes possible to evaluate various phenomena related to the hot-deformation of austenite

Micromechanical Modelling of Microtexture Formation in Low Alloy Steel Bainite

2011 ◽  
Vol 172-174 ◽  
pp. 1228-1233
Author(s):  
Sophie Lubin ◽  
Anne Francoise Gourgues-Lorenzon ◽  
Brigitte Bacroix ◽  
Hélène Réglé
Keyword(s):  
Micromechanical Model ◽  
Model Parameters ◽  
Low Alloy Steels ◽  
Obvious Effect ◽  
Austenite Grain ◽  
Shape Strain ◽  
Model Predictions ◽  
Alloy Steels ◽  
Upper Bainite ◽  
Parent Austenite

A micromechanical model was developed to account for the particular microtexture of upper bainite in low alloy steels, i.e. the non-random spatial distribution of variants within a given former austenite grain. A self-consistent scheme and an Eshelby approach, considering both transformation shape strain and viscoplastic strain as eigenstrains, was applied to estimate coupling between parent austenite and two or more bainite variants without any applied stress. Model predictions concerning self-accommodation between variants are sensitive to the plane of the first “lattice invariant shear” in the crystallographic model used to determine the shape strain. No obvious effect of the constitutive equations of phases and of the other model parameters was found.

Crystallographic Features of Low-Carbon Bainite Formed under Non-Isothermal Conditions

2013 ◽  
Vol 762 ◽  
pp. 110-115 ◽  
Author(s):  
S.N. Panpurin ◽  
Nikolay Y. Zolotorevsky ◽  
Yuri F. Titovets ◽  
A.A. Zisman ◽  
E.I. Khlusova
Keyword(s):  
Cooling Rate ◽  
Electron Backscatter Diffraction ◽  
Bainitic Ferrite ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Orientation Data ◽  
Austenite Grain ◽  
Low Carbon Bainite ◽  
Backscatter Diffraction ◽  
Parent Austenite

The effects of cooling rate and austenite structure on bainite formation was investigated by means of electron backscatter diffraction analysis and processing of obtained orientation data. Variant pairing tendency of bainitic ferrite was found to depend on the austenite grain size, austenite plastic deformation and cooling rate. In the bainite formed at low cooling rate the variant pairs having the same Bain axis correspondence are more frequent, while at high cooling rate the variant pairs having the same parallel correspondence of close-packed planes are formed side by side preferably. At the same time, these features are influenced significantly by structural state of parent austenite.

Morphology and Texture of Chemical-Vapour-Deposited TiN Films

1997 ◽  
Vol 472 ◽  
Author(s):  
Noboru Yoshikawa ◽  
Shoji Taniguchi ◽  
Atsushi Kikuchi
Keyword(s):  
Crystal Orientation ◽  
Chemical Vapour ◽  
Deposition Process ◽  
Grain Structure ◽  
Similar Time ◽  
Tin Films ◽  
Grain Structures ◽  
Structure Morphology ◽  
Columnar Grains ◽  
Zone Ii

ABSTRACTTiN films were obtained by Chemical Vapour Depositon (CVD) under different deposition conditions. Their grain structure, morphology and preferred crystal orientation were investigated. It was observed that well-defined columnar grams developed under conditions of atmospheric thermal CVD, giving rise to strong preferred orientations. In this study, grain structures of CVD-TiN films were classified with respect to the substrate temperature. Films of zone I structure were obtained at 1173K (0.35Tm), and those of zone II were obtained at 1223K (0.38Tm). Crystal shape of the zone II columnar grains was influenced by the partial pressure of TiCl4 (PTiCl4), and the crystal orientation of films was related to the crystal shapes. Columnar grains increased their thickness during deposition process under conditions of low PTiC14 and high temperature (>1250K). The increase rate of grain size had a similar time dependence to that of normal grain growth. The “quadrangular-shaped” and “star-shaped” columnar crystals were formed. They consisted of several crystals and contained twins. Their microstructures were observed in relation to their crystallographic features.

Tempering of Direct Quenched Low-Alloy Ultra-High-Strength Steel, Part I – Microstructure

2014 ◽  
Vol 922 ◽  
pp. 316-321 ◽  
Author(s):  
Antti J. Kaijalainen ◽  
Sakari Pallaspuro ◽  
David A. Porter
Keyword(s):  
Grain Size ◽  
Low Carbon Steel ◽  
High Strength ◽  
Steel Part ◽  
Grain Structure ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Direct Quenching ◽  
Austenite Grain ◽  
Effective Grain Size

The direct quenching of low-carbon steel has been shown to be an effective way of producing ultra-high-strength, tough structural steels in the as-quenched state without tempering. However, in the present study, the influence of tempering at 500 °C has been studied in order to evaluate the possibilities of widening the range of strengths that can be produced from a single base composition. The chosen composition was 0.1C-0.2Si-1.1Mn-0.15Mo-0.03Ti-0.002B. In order to compare direct quenching with conventional quenching, two pre-quench austenite states were studied: a thermomechanically rolled, non-recrystallized, pancaked austenite grain structure and a recrystallized, equiaxed grain structure. Quenched and quenched-and-tempered microstructures were studied using FESEM and FESEM-EBSD. The as-quenched microstructures of the reheated and quenched and direct quenched specimens were fully martensitic and martensitic-bainitic, respectively. In both cases, tempering made the needle-shaped auto-tempered carbides of the as-quenched materials more spherical. In the case of the direct quenched (DQ) material, tempering led to a notable increase in the size of the grain boundary carbides. Prior austenite grain size and effective grain size after quenching were larger in the case of reheated and quenched material (RQ). Tempering had no effect on effective grain size. The crystallographic texture of the DQ material showed strong {112}<131> and {554}<225> components. The RQ material also contained the same components, but it also contained an intense {110}<110> and {011}<100> components. The effects of these microstructural changes on tensile, impact toughness and fracture toughness are described in part II.

scholarly journals Effect of Austenitising and Deformation Temperatures on Dynamic Recrystallisation in Nb-Ti Microalloyed Steel

2013 ◽  
Vol 753 ◽  
pp. 431-434 ◽  
Author(s):  
Andrii G. Kostryzhev ◽  
Abdullah Al Shahrani ◽  
Chen Zhu ◽  
Simon P. Ringer ◽  
Elena V. Pereloma
Keyword(s):  
Microalloyed Steel ◽  
Solute Drag ◽  
Grain Structure ◽  
Temperature Deformation ◽  
Mechanical Processing ◽  
Austenite Grain ◽  
Dynamic Recrystallisation ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Gleeble 3500

An investigation into the influence of the reheat temperature and the austenite deformation temperature on Nb precipitation and recrystallisation kinetics was carried out for a steel containing 0.081C–0.021Ti–0.064Nb (wt. %). Thermo-mechanical processing was carried out using a Gleeble 3500 simulator. The austenite grain structure was correlated to the dispersive properties of Nb atom clustering and precipitation. Irrespective of the reheat temperature, deformation to 0.75 strain at 1075 °C produced a fully recrystallised austenitic microstructure. After deformation at 975 °C, only partial recrystallisation was observed in the samples reheated to the higher temperature, whereas samples reheated to the lower temperature were fully recrystallised. The influence of solute drag and particle pinning effects on the recrystallisation rate is discussed.

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