Neutron Diffraction Analysis of Load Transfer in DP 600 Steel During In Situ Tensile Tests

2011 ◽  
Vol 681 ◽  
pp. 31-36
Author(s):  
Marc Seefeldt ◽  
Steven Dillien ◽  
Uwe Stuhr
Keyword(s):  
Neutron Diffraction ◽  
Inflection Point ◽  
Load Transfer ◽  
Volume Fraction ◽  
Tensile Tests ◽  
Martensite Phase ◽  
Lattice Plane ◽  
Hard Phase ◽  
Plastic Part

The load transfer among ferrite orientations and between ferrite and martensite was analysed in DP 600 steel by means of neutron diffraction duringin situtensile tests on the multiple pulse overlap time-of-flight strain scanner POLDI. The material had 0.07 wt% C and a martensite volume fraction of 15%.In situtests were done in “Young” as well as in “Poisson setup”. The martensite phase could not be probed due to its low tetragonality. The curves of the lattice plane strains as a function of the externally applied macroscopic stress reveal (1) plastic relaxations of transformation and intergranular stresses in the compliant <100> oriented grains, and (2) a second inflection point in the fully plastic part indicating the onset of plastic deformation of the hard phase.

Stress Induced Martensitic Transformation in Shape Memory Alloys Studied by In-Situ Neutron Diffraction Techniques

2000 ◽  
Author(s):  
P. Šittner ◽  
V. Novák ◽  
P. Lukáš ◽  
D. Neov
Keyword(s):  
Martensitic Transformation ◽  
Neutron Diffraction ◽  
Shape Memory ◽  
Smart Materials ◽  
Hybrid Composites ◽  
Tensile Tests ◽  
Internal Stresses ◽  
Lattice Plane ◽  
In Situ Neutron Diffraction

Abstract Shape memory alloy (SMA) elements are being embedded in smart materials and hybrid composites as actuating and/or sensing elements responding to the stress and temperature stimuli. In order to design smart composites, in-situ experimental information about evolution of internal stresses and phase fractions in the embedded SMA elements and internal stresses in neighboring matrix during actuation cycles would be of interest. Such experimental data have to be obtained nondestructively from the microscopic particles or fibres deep in the bulk specimens exposed to stress and/or thermal variations. In-situ neutron diffraction experimental techniques fulfill in principle these requirements. However, reliable evaluation of internal stresses from neutron diffraction experiments in the smart SMA composites can be made only after the lattice plane responses of monolithic SMAs in thermomechanical cyclic loads are fully understood. In this paper, the results of the in-situ investigations of stress induced martensitic transformation (SIMT) in tensile tests carried out on monolithic CuAlZnMn SMA polycrystal are reported, and the observed lattice plane responses are interpreted using a selfconsistent model of SMA polycrystal.

scholarly journals Low-carbon cast microalloyed steel intercritically heat-treated at different temperatures: microstructure and mechanical properties

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Hadi Torkamani ◽  
Shahram Raygan ◽  
Carlos Garcia Mateo ◽  
Yahya Palizdar ◽  
Jafar Rassizadehghani ◽  
...  
Keyword(s):  
Carbon Content ◽  
Volume Fraction ◽  
Block Size ◽  
Tensile Tests ◽  
Total Elongation ◽  
Martensite Phase ◽  
Low Carbon ◽  
Steel Increase ◽  
Different Temperatures ◽  
The Impact

AbstractIn this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact energy even decreased from 12 to 9 J due to the brittleness of the martensite phase. The results of the tensile tests indicate that by increasing the IHT temperature, the yield and ultimate tensile strengths of the DP steel increase from 493 to 770 MPa, and from 908 to 1080 MPa, respectively, while the total elongation decreases from 9.8 to 4.5%. In contrast to the normalized sample, formation of martensite in the DP steels could eliminate the yield point phenomenon in the tensile curves, as it generates free dislocations in adjacent ferrite.

Localization of Stresses in Polycrystalline Grains Measured by Neutron Diffraction and Predicted by Self-Consistent Model

2011 ◽  
Vol 681 ◽  
pp. 103-108
Author(s):  
Anita Gaj ◽  
Lea le Joncour ◽  
Andrzej Baczmanski ◽  
Sebastian Wroński ◽  
Benoit Panicaud ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Load Transfer ◽  
Diffraction Method ◽  
Lattice Strains ◽  
Consistent Model ◽  
Self Consistent ◽  
Main Component ◽  
Critical Resolved Shear Stress ◽  
Elastic Lattice

Time of flight neutron diffraction method was applied to measure elastic lattice strains in austenitic steel during "in situ" tensile test. Comparing experimental data with self-consistent model, the critical resolved shear stress and hardening parameters were determined for polycrystalline grains. The result allowed us to determine the main component of the stress localization tensor, relating the rate of grain stress with the applied macrostress rate. The evolution of concentration tensor in function of the applied macrostress was analyzed. Finally, the load transfer between grains during yielding of the sample was studied.

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.

Dissolution of Cementite Plates by Drawing, Re-Precipitation with Annealing and Corresponding Changes in Tensile Behavior in a Pearlite Steel

2006 ◽  
Vol 118 ◽  
pp. 27-30
Author(s):  
Y. Shiota ◽  
A. Kanie ◽  
Yo Tomota ◽  
Stefanus Harjo ◽  
Atsushi Moriai ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Load Transfer ◽  
Tensile Loading ◽  
Strengthening Mechanism ◽  
Tensile Behavior ◽  
Microstructural Change ◽  
Subsequent Annealing ◽  
Main Mechanism ◽  
In Situ Neutron Diffraction

The microstructural change with drawing and subsequent annealing for a patented pearlite steel was investigated by means of neutron diffraction. The dissolution of cementite plates with drawing and re-precipitation of spherical cementite particles with annealing after sever drawing were observed. In situ neutron diffraction during tensile loading was performed and it is revealed that the strengthening mechanism of the specimen without cementite differs from that for a ferrite-cementite steel where the load transfer is a main mechanism. The possible strengthening mechanism for the heavily drawn specimen is proposed.

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 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.

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