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.

NUMERICAL MODELING OF PHASE TRANSFORMATION DURING GRINDING PROCESS

2017 ◽  
Vol 79 (5) ◽  
Author(s):  
Syed Mushtaq Ahmed Shah ◽  
M. A. Khattak ◽  
Muhammad Asad ◽  
Javed Iqbal ◽  
Saeed Badshah ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Thermal Stresses ◽  
Heating Temperature ◽  
Temperature History ◽  
Grinding Process ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Heating And Cooling

The rapid heating and cooling in a grinding process may cause phase transformations. This will introduce thermal strains and plastic strains simultaneously in a workpiece with substantial residual stresses. The properties of the workpiece material will change when phase transformation occurs. The extent of such change depends on the temperature history experienced and the instantaneous thermal stresses developed. To carry out a reliable residual stress analysis, a comprehensive modelling technique and a sophisticated computational procedure that can accommodate the property change with the metallurgical change of material need to be developed. The objective of this work is to propose a simplified model to predict phase evolution during given temperature history for heating and cooling as encountered during grinding process. The numerical implementation of the proposed model is carried out through the developed FORTRAN subroutine called PHASE using the FEM commercial software Abaqus®/standard. Micro-structural constituents are defined as state variables. They are computed and updated inside the subroutine PHASE. The heating temperature is assumed to be uniform while the cooling characteristics in relation to phase transformations are obtained from the continuous cooling transformation (CCT) diagram of the given material (here AISI 52100 steel). Four metallurgical phases are assumed for the simulations: austenite, pearlite, bainite, and martensite. It was shown that at low cooling rates high percentage of pearlite phase is obtained when the material is heated and cooled to ambient temperature. Bainite is formed usually at medium cooling rates. Similarly at high cooling rates maximum content of martensite may be observed. It is also shown that the continuous cooling transformation kinetics may be described by plotting the transformation temperature, directly against the cooling rate as an alternative to the continuous cooling transformation diagram. The simulated results are also compared with experimental results of Wever [20] and Hunkle [21] and are found to be in a very good agreement. The model may be used for further thermo-mechanical analysis coupled with phase transformation during grinding process.

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

Power characteristics of spinel cathodes correlated with elastic softness and phase transformation for high-power lithium-ion batteries

2017 ◽  
Vol 5 (7) ◽  
pp. 3404-3411 ◽  
Author(s):  
Jin-Myoung Lim ◽  
Rye-Gyeong Oh ◽  
Woosuk Cho ◽  
Kyeongjae Cho ◽  
Maenghyo Cho ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Electrochemical Properties ◽  
Phase Transformations ◽  
Lithium Ion Batteries ◽  
High Power ◽  
Lithium Ion ◽  
Transformation Kinetics ◽  
Power Characteristics ◽  
Phase Transformation Kinetics ◽  
Mechanical Deformations

We present the phase transformation kinetics associated with mechanical deformations and electrochemical properties of LiNi0.5Mn1.5O4 (LNMO) and LiNi0.5Mn1.5−xTixO4 (LNMTO) that elucidate the correlation between power characteristics, mechanical deformations, and phase transformations.

Modeling and Simulation of Phase Transformation during Grinding

2011 ◽  
Vol 223 ◽  
pp. 743-753 ◽  
Author(s):  
Michael Duscha ◽  
Atilim Eser ◽  
Fritz Klocke ◽  
Christoph Broeckmann ◽  
Hagen Wegner ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Surface Layer ◽  
Residual Stresses ◽  
Temperature History ◽  
Grinding Process ◽  
Thermal Loads ◽  
Transformation Kinetics ◽  
Workpiece Material ◽  
Holistic Model ◽  
Phase Transformation Kinetics

The grinding process is one of the most important finishing processes in production industry. During the grinding process the workpiece is subjected to mechanical and thermal loads. They can induce thermal damages in terms of phase transformation due to critical temperature history. A holistic model helps to describe and predict the influence of these loads on the residual stresses in the surface layer. In this paper, a very promising approach using the Finite Element Method (FEM) to simulate the surface grinding process in terms of thermal and mechanical loads during grinding of hardened and tempered steels with vitrified bonded CBN grinding wheels is introduced. The investigations were conducted for deep, pendulum and speed stroke grinding. The change of workpiece material properties was modelled as a function of temperature and phase history. The results lead to the necessary time depending temperature distribution within the surface layer. Hence, the phase transformation can be calculated. The FEM software "Sysweld" was used to analyze the phase transformation kinetics. Hence, the size of the rehardened zone after grinding can be predicted. The evaluation of the FEM model with micrographs of ground workpiece specimens showed a strong correlation for different grinding parameters. Based on the understanding of mechanical and thermal loads as well as phase transformation kinetics in the surface layers the resulting residual stresses can be determined.

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.

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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