scholarly journals Investigating the Difference in Mechanical Stability of Retained Austenite in Bainitic and Martensitic High-Carbon Bearing Steels using in situ Neutron Diffraction and Crystal Plasticity Modeling

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 482 ◽  
Author(s):  
Rohit Voothaluru ◽  
Vikram Bedekar ◽  
Dunji Yu ◽  
Qingge Xie ◽  
Ke An ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Crystal Plasticity ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
High Carbon ◽  
Martensitic Matrix ◽  
Bearing Steels ◽  
In Situ Neutron Diffraction

In situ neutron diffraction of the uniaxial tension test was used to study the effect of the surrounding matrix microstructure on the mechanical stability of retained austenite in high-carbon bearing steels. Comparing the samples with bainitic microstructures to those with martensitic ones, it was found that the retained austenite in a bainitic matrix starts transforming into martensite at a lower strain compared to that within a martensitic matrix. On the other hand, the rate of transformation of the austenite was found to be higher within a martensitic microstructure. Crystal plasticity modeling was used to analyze the transformation phenomenon in these two microstructures and determine the effect of the surrounding microstructure on elastic, plastic, and transformation components of the strain. The results showed that the predominant difference in the deformation accumulated was from the transformation strain and the critical transformation driving force within the two microstructures. The retained austenite was more stable for identical loading conditions in case of martensitic matrix compared to the bainitic one. It was also observed that the initial volume fraction of retained austenite within the bainitic matrix would alter the onset of transformation to martensite, but not the rate of transformation.

In Situ Neutron Diffraction Analysis of Phase Transformation Kinetics in TRIP Steel

2005 ◽  
Vol 502 ◽  
pp. 339-344 ◽  
Author(s):  
Jozef Zrník ◽  
O. Muránsky ◽  
Petr Lukáš ◽  
Petr Šittner ◽  
Z. Nový
Keyword(s):  
Neutron Diffraction ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Internal Stresses ◽  
Austenite Transformation ◽  
Austenite Stability ◽  
Retained Austenite Stability ◽  
In Situ Neutron Diffraction

The precise characterization of the multiphase microstructure of low alloyed TRIP steels is of great importance for the interpretation and optimisation of their mechanical properties. In-situ neutron diffraction experiment was employed for monitoring of conditioned austenite transformation to ferrite, and also for retained austenite stability evaluation during subsequent mechanical loading. The progress in austenite decomposition to ferrite is monitored at different transformation temperatures. The relevant information on the course of transformation is extracted from neutron diffraction spectra. The integrated intensities of austenite and ferrite neutron diffraction profiles over the time of transformation are then assumed as a measure of the volume fractions of both phases in dependence on transformation temperature. Useful information was also obtained on retained austenite stability in TRIP steel during mechanical testing. The in-situ neutron diffraction experiments were conducted at two different diffractometers to assess the reliability of neutron diffraction technique in monitoring the transformation of retained austenite during room temperature tensile test. In both experiments the neutron investigation was focused on the volume fraction quantification of retained austenite as well as on internal stresses rising in structure phases due to retained austenite transformation.

Deformation Behaviour of TRIP Steel Monitoring by in-Situ Neutron Diffraction

2011 ◽  
Vol 465 ◽  
pp. 390-394 ◽  
Author(s):  
Jozef Zrník ◽  
Ondrej Muránsky ◽  
Petr Šittner ◽  
E.C. Oliver
Keyword(s):  
Neutron Diffraction ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Deformation Behaviour ◽  
Tensile Load ◽  
Phase Evolution ◽  
In Situ Neutron Diffraction

The paper presents results of in-situ neutron diffraction experiments aimed on monitoring the phase evolution and load distribution in TRIP steel when subjected to tensile loading. Tensile deformation behaviour of TRIP steel with different initial microstructures showed that the applied tensile load is redistributed at the yield point and the harder retained austenite (Feγ) bears larger load then ferrite (Feα) matrix. After load partioning is finished, macroscopic yielding comes through simultaneous activity of the martensite transformation (in the austenite) and plastic deformation process in ferrite. The steel with higher volume fraction of retained austenite and less stronger ferrite appears to be a better TRIP steel having efficient structure for better plasticity purpose.

scholarly journals In-situ Neutron Diffraction Analysis of Crystal Plasticity of Retained Austenite in Bearing Steel

2017 ◽  
Vol 207 ◽  
pp. 1958-1963 ◽  
Author(s):  
Vikram Bedekar ◽  
Rohit Voothaluru ◽  
Qingge Xie ◽  
Alexandru Stoica ◽  
R. Scott Hyde ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Analysis ◽  
Crystal Plasticity ◽  
Retained Austenite ◽  
Bearing Steel ◽  
Neutron Diffraction Analysis ◽  
In Situ Neutron Diffraction

Thermal and mechanical stability of retained austenite in high carbon steel: An in - situ investigation

2016 ◽  
Vol 163 ◽  
pp. 209-213 ◽  
Author(s):  
Abhilash Molkeri ◽  
Farshid Pahlevani ◽  
Irene Emmanuelawati ◽  
Veena Sahajwalla
Keyword(s):  
Carbon Steel ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
High Carbon Steel ◽  
High Carbon ◽  
In Situ Investigation

scholarly journals Tracing Phase Transformation and Lattice Evolution in a TRIP Sheet Steel under High-Temperature Annealing by Real-Time In Situ Neutron Diffraction

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 360 ◽  
Author(s):  
Dunji Yu ◽  
Yan Chen ◽  
Lu Huang ◽  
Ke An
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Neutron Diffraction ◽  
Real Time ◽  
Retained Austenite ◽  
Sheet Steel ◽  
Carbon Diffusion ◽  
Structure Evolution ◽  
In Situ Neutron Diffraction

Real-time in situ neutron diffraction was used to characterize the crystal structure evolution in a transformation-induced plasticity (TRIP) sheet steel during annealing up to 1000 °C and then cooling to 60 °C. Based on the results of full-pattern Rietveld refinement, critical temperature regions were determined in which the transformations of retained austenite to ferrite and ferrite to high-temperature austenite during heating and the transformation of austenite to ferrite during cooling occurred, respectively. The phase-specific lattice variation with temperature was further analyzed to comprehensively understand the role of carbon diffusion in accordance with phase transformation, which also shed light on the determination of internal stress in retained austenite. These results prove the technique of real-time in situ neutron diffraction as a powerful tool for heat treatment design of novel metallic materials.

Deformation Behaviour of TRIP Steel Monitored by In Situ Neutron Diffraction

2014 ◽  
Vol 939 ◽  
pp. 25-30
Author(s):  
Jozef Zrník ◽  
Ondrej Muránsky ◽  
Petr Sittner
Keyword(s):  
Neutron Diffraction ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Deformation Behaviour ◽  
Tensile Load ◽  
Ferrite Matrix ◽  
Granular Bainite

The paper presents results ofin-situneutron diffraction experiments aimed on monitoring the phase evolution and load distribution in transformation induced plasticity (TRIP) steel when subjected to tensile loading. Tensile deformation behaviour of two TRIP-assisted multiphase steel with slightly different microstructures resulted from different thermo-mechanical treatments applied was investigated byin-situneutron diffraction. The steel with lower retained austenite volume fraction (fγ=0.04) and higher volume fraction of needle-like bainite in the α-matrix exhibits higher yield stress (sample B, 600MPa) but considerably lower elongation in comparison to the steel with higher austenite volume fraction (fγ=0.08), granular bainite and ferrite matrix (sample A, 500 MPa). The neutron diffraction results showed that the applied tensile load is redistributed at the yielding point in a way that the retained austenite bears a significantly larger load than the α-matrix during the TRIP steel deformation. Steel sample with higher volume fraction of retained austenite and less strong ferrite matrix proved to be a better TRIP steel with respect to strength, ductility and the side effect of the strain induced austenite-martensite transformation. The transforming retained austenite in time of loading provides potential for higher ductility of experimental TRIP steel but at the same time acts as a reinforcement phase during the further plastic deformation.TRIP steel, austenite conditioning, austenite transformation, structure, retained austenite, tensile deformation, neutron diffraction, load partitioning, mechanical properties.

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.

Investigation of Forming Conditions on Microstructure Development and Mechanical Stability of Trip Steel

2008 ◽  
Vol 575-578 ◽  
pp. 1396-1401
Author(s):  
Jozef Zrník ◽  
O. Murnsky ◽  
Peter Horňak ◽  
Martin Fujda
Keyword(s):  
Trip Steel ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
Thermomechanical Processing ◽  
Structural Characteristics ◽  
Transformation Induced Plasticity ◽  
In Situ Neutron Diffraction ◽  
Neutron Diffraction Technique ◽  
Kinetics Of

Experimental simulations of thermomechanical processing (TM) using press forging of Si-Mn TRIP (transformation induced plasticity) steel were performed. In order to rationalize the retained austenite (RA) volume fraction, six TM schedules were employed at experiment where different austenite conditioning was considered. The various multiphase structure characteristics were obtained after of TM processing, with different volume fraction of ferrite, bainite and RA. The modification of structural characteristics influenced the mechanical properties of TRIP steel. The present work also focuses on monitoring of RA transformation during mechanical incremental straining using in situ neutron diffraction technique. This method is used to characterize the kinetics of RA transformation and its stability during the straining.

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