Martensite phase stress and the strengthening mechanism in TRIP steel by neutron diffraction (original) (raw)
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IOP Conference Series: Materials Science and Engineering, 2019
Multi-phase steels showing transformation induced plasticity (TRIP), can exhibit an excellent combination of high strength and good ductility by the aid of martensitic transformation during deformation. Even though TRIP-assisted multi-phase steels have been widely used in industry, the role of each phase in the enhancement of mechanical properties is still unclear given their complicated microstructures. In order to understand better the nature of the TRIP effect, the mechanical interaction between different phases at the micro-scale should be clarified. In the present study, the mechanical behavior of a transformation induced plasticity (TRIP) assisted multi-phase steel, has been characterized by in-situ neutron diffraction during tensile testing. The result of strain partitioning between the different phases obtained from the in-situ neutron analysis revealed that the martensite phase took much more elastic strain than the ferrite and retained austenite phases, which suggests that...
Tensile behavior of TRIP-aided multi-phase steels studied by in situ neutron diffraction
Acta Materialia, 2004
TRIP-aided multi-phase steels were made by thermo-mechanically controlled process, where the ferrite grain size and the amount of the retained austenite were changed by controlling process conditions. The tensile behavior of four steels was studied by in situ neutron diffraction. It is found that the retained austenite bearing about 1.0 wt% C is plastically harder than the ferrite matrix. The steel with a ferrite grain size of %2.0 lm showed tensile strength of 1.1 GPa and a uniform elongation of 18.4%, in which stressinduced martensitic transformation occurs during plastic deformation but a considerable amount of austenite remains even after the onset of necking. It is concluded that the enhancement of uniform elongation is caused mainly by the work-hardening due to the hard austenite and martensite, where the contribution of the transformation strain is negligible.
TRIP Steel Deformation Behavior by Neutron Diffraction
MRS Proceedings, 2013
ABSTRACTDeformation behaviors of two TRIP-type multiphase steels with different carbon contents were studied by in situ neutron diffraction measurement during tensile deformation at RT. The tensile test was conducted in a step-load controlling manner during the elastic region, and in a continuous manner with a constant crosshead speed by an initial strain rate of 1.8×10-5 s-1 during the plastic region. Austenite grains were observed to bear higher phase stresses than ferrite grains in both steels. Austenite peak intensities started to decrease at the onsets of plastic deformation in both steels, showing the occurrence of stress induced martensitic transformations. Martensite peaks were carefully analyzed to estimate phase strains, and as the results martensite grains were found to bear largest phase stresses during plastic deformation.
ISIJ International, 2020
In situ neutron diffraction measurements of two low-alloy steels and a 304-type stainless steel during tensile and creep tests were performed at room temperature. Changes in the diffraction pattern, the integrated peak intensities of austenite (γ), and the peak positions of γ were analyzed and discussed to elucidate the relationship between intergranular stress in γ and the occurrence of martensitic transformation during deformation. Tensile loading experiments revealed that the susceptibility to martensitic transformation depended on the γ-(hkl) grains, where γ-(111) grains underwent martensitic transformation at the latest. The volume fractions of γ were found to decrease under an applied load but to remain almost unchanged under constant load in creep tests, where the lattice strains of γ-(hkl) grains were mostly unchanged. The γ-hkl dependence of the susceptibility to martensitic transformation was found to be controlled by the shear stress levels in γ-(hkl) grains, which were affected by the intergranular stress partitioning during deformation.
Applied Physics Letters, 2015
In-situ neutron diffraction during cyclic tension-compression loading ($þ3.5% to À2.8%) of a 17Mn-3Al-2Si-1Ni-0.06C steel that exhibits concurrent transformation and twinning -induced plasticity effects indicated a significant contribution of intragranular back stresses to the observed Bauschinger effect. Rietveld analysis revealed a higher rate of martensitic transformation during tension compared to compression. Throughout cycling, a 0 -martensite exhibited the highest phase strains such that it bears an increasing portion of the macroscopic load as its weight fraction evolves. On the other hand, the e-martensite strain remained compressive as it accommodated most of the internal strains caused by the shape misfit associated with the c!e and/or e!a 0 transformations. V C 2015 AIP Publishing LLC. [http://dx.Low stacking fault energy (SFE), high-Mn (15-30 wt. %) Transformation Induced Plasticity (TRIP) and Twinning Induced Plasticity (TWIP) steels are the current subject of intense world-wide research due to their unique combination of high strength and ductility with superior energy absorption properties. TRIP steels (SFE < 12 mJ/m 2 ) contain a metastable c-austenite (face centered cubic) which transforms to emartensite (hexagonal close packed) and/or a 0 -martensite (approximated as body centered cubic when tetragonality is minor (c/a $ 1) and cannot be resolved in the diffraction patterns) during room temperature deformation. TWIP steels (SFE $ 18-40 mJ/m 2 ) comprise a stable c phase that exhibits twinning along with slip upon straining. Alternatively, TRIP-TWIP steels (SFE ¼ 12-18 mJ/m 2 ) undergo concurrent martensitic transformation, twinning, and slip. 1 To this end, the present study tracks the deformation and phase transformation behavior of a TRIP-TWIP steel via in-situ neutron diffraction (ND) during cyclic (tension-compression) loading.
Acta Materialia, 2008
The deformation behaviour of two transformation induced plasticity (TRIP)-assisted steels with slightly different microstructures due to different thermo-mechanically controlled processing (TMCP) was investigated by the in situ neutron diffraction technique during tensile straining at room temperature and two elevated (50 and 100°C) temperatures. The essential feature of the TRIP deformation mechanism was found to be significant stress redistribution at the yield point. The applied tensile load is redistributed within the complex TRIP-steel microstructure in such a way that the retained austenite bears a significantly larger load than the ferrite-bainite a-matrix. The macroscopic yielding of the steel then takes place through the simultaneous cooperative activity of the austenite-to-martensite transformation in the austenite phase and plastic deformation in the a-matrix. It is concluded that, although its volume fraction is small, the martensitically transforming retained austenite phase dispersed within the a-matrix governs the plastic deformation of TRIP-assisted steels. Crown