Interaction Deformation / Precipitation / Phase Transformation in Nb Micro-Alloyed Steels

2011 ◽  
Vol 172-174 ◽  
pp. 735-740 ◽  
Author(s):  
Philippe Thibaux ◽  
Martin Liebeherr ◽  
Dominique De Avila Cossa
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Ferrite Phase ◽  
Transformation Kinetics ◽  
Continuous Cooling ◽  
Slowing Down ◽  
Phase Transformation Kinetics ◽  
Precipitation Phase ◽  
Soaking Temperature

Characterization of the phase transformation of Nb-micro-alloyed steels has to be performed taking into account the effect of deformation and precipitation. In the present investigation, the austenite to ferrite phase transformation is characterized in continuous cooling experiments after deformation at high temperature. The resulting phase transformation kinetics and microstructure showed an influence of the soaking temperature. Detailed investigations of the possible causes of the change of mechanism of phase transformation indicate that the amount of niobium in solution correlates with the slowing down in phase transformation kinetics.

Modeling Phase Transformation Kinetics and Their Effect on Hardness and Hardness Depth in Laser Hardening of Hypoeutectoid Steel

2015 ◽  
Author(s):  
Suhash Ghosh ◽  
Chittaranjan Sahay
Keyword(s):  
Thermal Analysis ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Laser Hardening ◽  
Temperature History ◽  
Transformation Kinetics ◽  
Continuous Cooling ◽  
Phase Transformation Kinetics ◽  
Hardness Depth ◽  
Hypoeutectoid Steel

Much research has been done to model laser hardening phase transformation kinetics. In that research, assumptions are made about the austenization of the steel that does not translate into accurate hardness depth calculations. The purpose of this paper is to develop an analytical method to accurately model laser hardening phase transformation kinetics of hypoeutectoid steel, accounting for non-homogeneous austenization. The modeling is split into two sections. The first models the transient thermal analysis to obtain temperature time-histories for each point in the workpiece. The second models non-homogeneous austenization and utilizes continuous cooling curves to predict microstructure and hardness. Non-homogeneous austenization plays a significant role in the hardness and hardness depth in the steel. A finite element based three-dimensional thermal analysis in ANSYS is performed to obtain the temperature history on three steel workpieces for laser hardening process with no melting; AISI 1030, 1040 and 1045 steels. This is followed by the determination of microstructural changes due to ferrite and pearlite transformation to austenite during heating and the subsequent austenite to martensite and other diffusional transformations during cooling. Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation is used to track the phase transformations during heating, including the effects of non-homogenous austenitization. The solid state nodal phase transformations during cooling are monitored on the material’s digitized Continuous Cooling Transformation (CCT) curve through a user defined input file in ANSYS for all cooling rates within the Heat Affected Zone (HAZ). Material non-linearity is included in the model by including temperature dependent thermal properties for the material. The model predictions for hardness underneath the laser and the HAZ match well with the experimental results published in literature.

scholarly journals Dilatometric Analysis of the Austenite Decomposition in Undeformed and Deformed Low-Carbon Structural Steel

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5443
Author(s):  
Mateusz Morawiec ◽  
Adam Skowronek ◽  
Mariusz Król ◽  
Adam Grajcar
Keyword(s):  
Phase Transformation ◽  
Structural Steel ◽  
Transformation Product ◽  
Low Carbon ◽  
Transformation Kinetics ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Phase Transformation Kinetics ◽  
Microscopic Studies ◽  
Carbon Structural Steel

This paper aims to analyze the effect of deformation on the phase transformation kinetics of low-carbon structural steel. The steel used for the investigation was subjected to two different dilatometric analyses using a DIL 805A/D device. The first analysis was to determine the phase transformation kinetics without deformation of austenite before cooling. Then, the analysis under deformation conditions was conducted to investigate the deformation effect on the transformation kinetics. Microscopic studies by light microscopy were performed. The essential part of the research was hardness analysis for different cooling rates and the creation of continuous-cooling-transformation (CCT) and deformation continuous-cooling-transformation (DCCT) diagrams. It was found that the deformation of the samples before cooling increases a diffusion rate in the austenite resulting in the corresponding increase of ferritic, pearlitic, and bainitic start temperatures, as well as shifting the austenite transformation product regions to a longer time. The increase of the transformation area and a decrease in grain size are observed for the deformed samples.

β phase transformation kinetics in Ti60 alloy during continuous cooling

2013 ◽  
Vol 576 ◽  
pp. 108-113 ◽  
Author(s):  
Feng Sun ◽  
Jinshan Li ◽  
Hongchao Kou ◽  
Bin Tang ◽  
Yi Chen ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Transformation Kinetics ◽  
Continuous Cooling ◽  
Β Phase ◽  
Phase Transformation Kinetics

Microstructural formation in Ti alloys: In-situ characterization of phase transformation kinetics

JOM ◽  
2007 ◽  
Vol 59 (1) ◽  
pp. 54-58 ◽  
Author(s):  
E. Aeby-Gautier ◽  
F. Bruneseaux ◽  
J. Da Costa Teixeira ◽  
B. Appolaire ◽  
G. Geandier ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Transformation Kinetics ◽  
In Situ Characterization ◽  
Ti Alloys ◽  
Phase Transformation Kinetics

scholarly journals Solid state phase transformation kinetics in Zr-base alloys

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. R. Massih ◽  
Lars O. Jernkvist
Keyword(s):  
Phase Transformation ◽  
Solid State ◽  
Zirconium Alloys ◽  
Excess Oxygen ◽  
Transformation Kinetics ◽  
Fuel Cladding ◽  
Reactor Accident ◽  
Phase Transformation Kinetics ◽  
Solid State Phase Transformation ◽  
Water Reactors

AbstractWe present a kinetic model for solid state phase transformation ($$\alpha \rightleftharpoons \beta$$ α ⇌ β ) of common zirconium alloys used as fuel cladding material in light water reactors. The model computes the relative amounts of $$\beta$$ β or $$\alpha$$ α phase fraction as a function of time or temperature in the alloys. The model accounts for the influence of excess oxygen (due to oxidation) and hydrogen concentration (due to hydrogen pickup) on phase transformation kinetics. Two variants of the model denoted by A and B are presented. Model A is suitable for simulation of laboratory experiments in which the heating/cooling rate is constant and is prescribed. Model B is more generic. We compare the results of our model computations, for both A and B variants, with accessible experimental data reported in the literature covering heating/cooling rates of up to 100 K/s. The results of our comparison are satisfactory, especially for model A. Our model B is intended for implementation in fuel rod behavior computer programs, applicable to a reactor accident situation, in which the Zr-based fuel cladding may go through $$\alpha \rightleftharpoons \beta$$ α ⇌ β phase transformation.

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