In Situ Deformation Behavior of Retained Austenite in TRIP Steel

Deformation behavior of nanocomposites based on an ethylene/1-octene copolymerand multiwalled carbon nanotube (CNT) was investigated by means of an atomic forcemicroscope (AFM). Via a special tensile module integrated to an optical microscope, it waspossible to record the stress-strain diagrams of the composites using miniaturized tensilespecimens. By analyzing strain induced structural changes occurring at differentsuccessively applied loads, it was possible to correlate the deformation mechanismsoccurring on various length scales (i.e. at macroscopic, microscopic as well as nanoscopiclevels) to different degrees of deformation. It was noteworthy that, contrasting theproperties of other nanocomposites described so far in the literature, both the strength andtoughness of the composites were found to enhance. It was found that the deformation of thecomposite on nanoscopic scale was inhomogeneous owing to anisotropic properties of theCNTs and their alignments. After unloading the sample, the nanostructure of the originalmaterial was fully regenerated explaining the macroscopically observed elastomericproperties.Keywords: Ethylene/1-octene copolymer; CNT; Deformation mechanism; AFM; In situ deformation testsDOI: 10.3126/jncs.v26i0.3626Journal of Nepal Chemical SocietyVol. 26, 2010Page: 22-30

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Deformation Behaviour of TRIP Steel Monitored by In Situ Neutron Diffraction

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.939.25 ◽

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.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.502.339 ◽

2005 ◽

Vol 502 ◽

pp. 339-344 ◽

Cited By ~ 7

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.

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Thermomechanical Processing Controlling the Austenite Transformation in Si – Mn TRIP Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.345-346.41 ◽

2007 ◽

Vol 345-346 ◽

pp. 41-44

Author(s):

Jozef Zrník ◽

Ondrej Muránsky ◽

Ondrej Stejskal ◽

Peter Horňak

Keyword(s):

Neutron Diffraction ◽

Trip Steel ◽

Tensile Testing ◽

Retained Austenite ◽

Thermomechanical Processing ◽

Deformation Behaviour ◽

Transformation Process ◽

Austenite Transformation ◽

Neutron Diffraction Technique

The paper deals with the deformation and transformation behaviour of thermomechanically (TM) treated low alloyed Si-Mn TRIP steel. The aim of this work was to investigate the contribution of the factors governing the deformation and transformation process of conditioned austenite. Variation in strain and temperature parameters of TM treatment of TRIP steel samples resulted in formation of different complex microstructures. The deformation behaviour of TRIP specimens of different multiphase structures was tested in incremental neutron diffraction in situ tensile testing. It was proved that neutron diffraction technique is very convenient method for retained austenite (RA) transformation of the retained austenite with respect to monitoring of transformation quantification of retained austenite and rising internal stress in structural phases.

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

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.465.390 ◽

2011 ◽

Vol 465 ◽

pp. 390-394 ◽

Cited By ~ 1

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.

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