Is There a Minimal Chemical Mechanism Underlying Classical Avrami-Erofe’ev Treatments of Phase-Transformation Kinetic Data?

2009 ◽  
Vol 21 (19) ◽  
pp. 4692-4705 ◽  
Author(s):  
Eric E. Finney ◽  
Richard G. Finke
Keyword(s):  
Phase Transformation ◽  
Kinetic Data ◽  
Chemical Mechanism ◽  
Transformation Kinetic ◽  
Phase Transformation Kinetic

Investigation of Effect of Phase Transformations on Mechanical Behavior of AISI 1010 Steel in Laser Forming

2005 ◽  
Vol 129 (1) ◽  
pp. 110-116 ◽  
Author(s):  
Yajun Fan ◽  
Zhishang Yang ◽  
Peng Cheng ◽  
Keith Egland ◽  
Lawrence Yao
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Volume Fraction ◽  
Constitutive Relationship ◽  
Laser Forming ◽  
Transformation Kinetic ◽  
Forming Process ◽  
Element Analysis ◽  
Relationship Of ◽  
Phase Transformation Kinetic

In laser forming, phase transformations in the heat affected zone take place under steep cooling rates and temperature gradients, and have a significant affect on the laser forming process and final mechanical properties of products. In this work, phase transformations during laser forming of AISI 1010 steel are experimentally and numerically investigated and the transient volume fraction of each available phase is calculated by coupling the thermal history from finite element analysis with a phase transformation kinetic model. Consequently, the flow stresses of material are obtained from the constitutive relationship of the phases, and the laser forming process is modeled considering the effect of work hardening, recrystallization and phase transformation. A series of carefully controlled experiments are also conducted to validate the theoretically predicted results.

Diffusion under a Stress in Metals and Interstitial Alloys

2011 ◽  
Vol 172-174 ◽  
pp. 1156-1163 ◽  
Author(s):  
Andrei V. Nazarov ◽  
Alexander Mikheev ◽  
Irina Valikova ◽  
Alexander Zaluzhnyi
Keyword(s):  
Phase Transformation ◽  
Low Temperatures ◽  
Diffusion Processes ◽  
Transformation Kinetic ◽  
Maximal Degree ◽  
Diffusion In Solids ◽  
Elastic Fields ◽  
Cubic Metals ◽  
Alloy Properties ◽  
Phase Transformation Kinetic

Elastic fields, generating by precipitates, cracks, dislocations and other defects of the structure, influence the diffusion processes. It leads to the alteration of the phase transformation kinetic, segregation formation and changes of the alloy properties. However, understanding the effects of strain on diffusion in solids is now limited. One of the chief aims of our approach is to obtain the general equations for the diffusion fluxes under strain that give the possibility of using these equations at low temperatures, as in this case, the strain influence on the diffusion fluxes is manifested in maximal degree. Recently some important generalization of our approach was done and equations for the vacancy fluxes in cubic metals were obtained. Now we have made the next step in the development of approach: general equations for the fluxes in interstitial alloys are obtained for different kinds of jumps in bcc and fcc structures. We are going to discuss the main features of the theory of diffusion under stress, to compare the equations for the fluxes and to present results of theory applications that are obtained with the help of computer simulations.

scholarly journals Theoretical Assessment on the Phase Transformation Kinetic Pathways of Multi-component Ti Alloys: Application to Ti-6Al-4V

2015 ◽  
Vol 37 (1) ◽  
pp. 53-64 ◽  
Author(s):  
Yanzhou Ji ◽  
Tae Wook Heo ◽  
Fan Zhang ◽  
Long-Qing Chen
Keyword(s):  
Phase Transformation ◽  
Transformation Kinetic ◽  
Ti Alloys ◽  
Theoretical Assessment ◽  
Phase Transformation Kinetic

scholarly journals Aging Behavior and Precipitation Analysis of Cu-Ni-Co-Si Alloy

Crystals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 435
Author(s):  
Xiangpeng Xiao ◽  
Jian Huang ◽  
Jinshui Chen ◽  
Hai Xu ◽  
Zhao Li ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Aging Process ◽  
Kinetic Curve ◽  
Kinetic Equations ◽  
Phase Region ◽  
Transformation Kinetic ◽  
Precipitation Kinetic ◽  
Two Phase ◽  
Transmission Electron ◽  
Co Addition

Cu-Ni-Si alloy with a different Co content was prepared by inductive melting and hot rolling. The alloy was solution treated at 950 °C for 1.5 h and aged at 450 °C, 500 °C, and 550 °C for different times. The phase diagram calculation and transmission electron microscopy was used to investigate the effect of Co addition on the aging precipitation behavior of the Cu-Ni-Si alloy. The phase transformation kinetics equation was calculated as well. The results show that, with the increase of aging temperature, the two-phase region of Fcc + Ni2Si in the Cu-Ni-Si ternary diagram would get wider. Some NixSiy phases would also form in the Cu-rich isothermal section. The addition of Co would replace part of Ni to form the (Ni, Co)2Si phase, which inhibits the spinodal decomposition process of the Cu-Ni-Si alloy during the aging process. The precipitated phase of the Cu-Ni-Si alloy with a high content of the Co element is more likely to grow with the extension of aging time. The phase transformation kinetic equations of the Cu-Ni-Si alloy at 450 °C and 500 °C showed good agreement with the experimental results. Furthermore, it can be seen from the precipitation kinetic curve the addition of the Co element accelerates precipitation in the aging process.

scholarly journals Size Effects in Residual Stress Formation during Quenching of Cylinders Made of Hot-Work Tool Steel

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Manuel Schemmel ◽  
Petri Prevedel ◽  
Ronald Schöngrundner ◽  
Werner Ecker ◽  
Thomas Antretter
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Tool Steel ◽  
Transformation Kinetic ◽  
Bainite Transformation ◽  
Thermomechanical Model ◽  
Component Size ◽  
Hot Work Tool Steel ◽  
Quenching Process ◽  
Stress Formation

The present work investigates the residual stress formation and the evolution of phase fractions during the quenching process of cylindrical specimens of different sizes. The cylinders are made of hot-work tool steel grade X36CrMoV5-1. A phase transformation kinetic model in combination with a thermomechanical model is used to describe the quenching process. Two phase transformations are considered for developing a modelling scheme: the austenite-to-martensite transformation and the austenite-to-bainite transformation. The focus lies on the complex austenite-to-bainite transformation which can be observed at low cooling rates. For an appropriate description of the phase transformation behaviour nucleation and growth of bainite are taken into account. The thermomechanical model contains thermophysical data and flow curves for each phase. Transformation induced plasticity (TRIP) is modelled by considering phase dependent Greenwood-Johnson parameters for martensite and bainite, respectively. The influence of component size on residual stress formation is investigated by the finite element package Abaqus. Finally, for one cylinder size the simulation results are validated by X-ray stress measurements.

A Computational Model for Phase Transformation-Temperature-Distortion Coupling of AISI 5120 Steel

2006 ◽  
Vol 118 ◽  
pp. 387-392 ◽  
Author(s):  
Seok Jae Lee ◽  
Young Kook Lee
Keyword(s):  
Heat Transfer ◽  
Phase Transformation ◽  
Kinetic Models ◽  
Transformation Temperature ◽  
Volume Fraction ◽  
Coupled Model ◽  
Avrami Equation ◽  
Transformation Kinetic ◽  
Phase Transformation Temperature ◽  
Finite Element Software

A coupled model for predicting phase transformation, temperature, and distortion of AISI 5120 steel occurring during heat treatment process has been developed. The phase transformation kinetic models were made using Johnson-Mehl-Avrami equation and the additivity rule based on theoretical thermodynamic model and experimental dilatometric data. Especially, the transformation strains measured during cooling were converted to the volume fraction of each phase for the kinetic models using a relation between transformation strain and atomic volume change. The heat transfer coefficients in quench media were calculated by inverse method of the heat transfer equation to the measured surface temperature history. To predict the temperature and distortion accurately, the thermal and mechanical data were used as a function of temperature and each phase based on the experimental data. The coupled model for phase transformation, temperature, and distortion has been implemented in the commercial finite element software ABAQUS as user subroutines. The calculated results by the coupled model were compared with the experimental ones.

Phase-Transformation Kinetics of TiO2 in TiO2/(O′+β′)-Sialon Multi-Phase Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 2318-2321
Author(s):  
Jian Yang ◽  
Xiang Xin Xue ◽  
Li Mei Pan ◽  
Mei Wang ◽  
Tai Qiu
Keyword(s):  
Phase Transformation ◽  
Kinetic Model ◽  
Raw Materials ◽  
Transformation Process ◽  
Transformation Kinetic ◽  
Order Kinetic ◽  
Weight Percentage ◽  
Tio2 Anatase ◽  
Additive Content ◽  
Kinetics Of

TiO2/(O′+β′)-Sialon multiphase ceramics with different phase composition of TiO2 were prepared by pressureless sintering under high-purity N2 atmosphere with (O′+β′)-Sialon powder and nano TiO2 (anatase) powder as raw materials, Yb2O3 or Tb2O3 as additive. For each sample, the weight percentage of anatase in TiO2 was calculated from XRD data and the kinetics of anatase-rutile transformation was investigated, wherein the emphasis was placed on the influence of Yb2O3 and Tb2O3. The results indicate that the added Tb2O3 and Yb2O3 serve the significant function of inhibition and promotion on the phase transformation, and the effects are enhanced and attenuated with increasing additive content, respectively. For the sample without additive, the transformation process follows apparent first-order kinetic model. The addition of Yb2O3 or Tb2O3 results in completely different transformation kinetic law. For the samples with Yb2O3 added, the transformation is an apparent second-order reaction, whereas a unique kinetic model, CA=kt1/2+C, is valid for the samples containing Tb2O3. In the two cases, the effect of the additive content on the transformation can be perfectly reflected by the apparent rate constant.

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