Identification of stress-induced nucleation sites for martensite in Fe-31.8 wt% Ni-0.02 wt% C alloy (original) (raw)
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Physica B-condensed Matter, 2007
Kinetical, morphological, crystallographical and several thermal properties of thermally induced martensite in the austenite phase of Fe-30% Ni-5% Cu alloy were investigated. Scanning electron microscope (SEM), transmission electron microscope (TEM) and differential scanning calorimetry (DSC) techniques were used during study. Kinetics of the transformation was found to be as athermal type. SEM and TEM observations revealed a 0 (BCC) martensite formation in the austenite phase of alloy by thermal effect. These thermally induced a 0 martensites exhibited a thin plate-like morphology with twinnings. r
New observations on formation of thermally induced martensite in Fe–30%Ni–1%Pd alloy
Bulletin of Materials Science, 2013
Kinetical, morphological, crystallographical and thermal characteristics of thermally induced martensite in an Fe-30%Ni-1%Pd alloy has been studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and X-ray diffraction method. Kinetics of transformation was found to be as athermal. SEM and TEM observations and X-ray method revealed α (bcc) martensite formation in the austenite phase of alloy by thermal effect. The crystallographic orientation relationship between austenite and α (bcc) martensite was found to be having Kurdjumov-Sachs (K-S) type relationship. In addition, the lattice parameters of austenite and martensite phases were calculated from X-ray diffraction patterns.
Journal of Alloys and Compounds, 2002
The present study considers X-ray characterization of the microstructures of deformation-induced martensites of Fe-Mn-C alloy powders of grain size |50 mm (hand-filed) having compositions 5.6, 5.8 and 6.0 Mn and 1.0 C (mass%). The cold-worked powders were further subjected to transformation at low temperatures close to M and the evolved phases were again characterized microstructurally. s The methodology applied for characterization involves Rietveld's whole X-ray profile fitting technique adopting the most recently developed software, MAUD (Materials Analysis Using Diffraction) which incorporates Popa model for crystallite (domain) size and microstrain (root mean square, r.m.s.) and preferred orientation of the crystallites. The analysis also considers lattice defect-related features of the microstructure viz. stacking, twin, compound fault probabilities and dislocation density value. The cold-worked powders (hand-filed at room temperature) revealed the highest degree of transformation with 47, 43 and 42% volume fractions of martensites with increasing Mn concentration which for the bulk state of the same alloys transformed at low temperatures are 36, 40 and 47%. The same deformed alloy powders when subjected to low temperature transformation, evolved a maximum of 60, 68 and 62% volume fractions of martensites at 170, 175 and 190 K. The analysis reveals the occurrence of a high propensity of stacking faults in the deformed austenites 22 23 1 2 1 3 22
Metal Science and Heat Treatment, 2017
In this study, kinetics, morphological and magnetic properties of thermal induced and pre-strain of austenite martensitic transformations in an Fe-30%Ni-3%Pd alloy were investigated. Effect of pre-strain to austenite phase above the M temperature and kinetics, morphological and magnetic properties of martensitic s transformations which was formed by below the M temperature after the pre-strain were investigated. s Kinetics of martensitic transformation (martensite start temperature (M), austenite start temperature (A) and s s austenite finish temperature (A)) were determined by Diferential Scanning Calorimetry (DSC). Kinetics of the f transformation was found to be as athermal type and M temperature decreased with increasing prestrain. 5% s and 10% pre-strain which was applied to austenite phase at room temperature formed slip lines. Martensite plates, which were broken and bent, formed by cooling the alloy after 5% prestrain and martensite plates which were decrescent formed by cooling after 10% pre-strain, observed by Scanning Electron Microscopy (SEM). The volume fraction of martensite and austenite phases, the hyperfine magnetic field of martensite phase and isomery shift values in Fe-30%Ni-3%Pd alloy have been determined by using Mössbauer Spectroscopy. The pre-strain which are influential on the transformation kinetics and the martensite plates morphology, increased the rate of martensite volume.
Characterization of martensite in Fe–25%Ni–15%Co–5%Mo alloy
Journal of Physics and Chemistry of Solids, 2009
Kinetic, morphological, crystallographical, magnetic and thermal characteristics of thermally induced martensite in Fe-25%Ni-15%Co-5%Mo alloy have been investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), Mössbauer spectrometer, and differential scanning calorimeter (DSC). Kinetics of the transformation was found to be athermal. Also only lenticular martensite morphology was observed during microscope observations. In addition, martensite start temperature (M s ) was determined as À63 1C from differential scanning calorimeter. On the other hand, Mössbauer spectra revealed a paramagnetic character for the austenite phase and a ferromagnetic character for thermally induced martensite phase.
Some characteristics of thermally induced martensite in Fe–30%Ni–3.6%Mo alloy
Materials Characterization, 2008
Kinetical, morphological and magnetic characteristics of thermally induced martensite in an Fe-30%Ni-3.6%Mo alloy has been studied by scanning electron microscopy, transmission electron microscopy and Mössbauer spectroscopy. Scanning electron microscope and transmission electron microscope observations revealed the occurrence of both athermal and isothermal martensitic transformation in the alloy. In addition, the magnetic properties of both the austenite and martensite phases were determined by the Mössbauer spectroscopy. The Mössbauer spectra showed a paramagnetic character for the austenite phase and an antiferromagnetic character for the martensite phase.
Two-Stage Martensitic Transformation in NiTi Alloys Caused by Stress Fields
Le Journal de Physique IV, 1997
It has been proved that the two-stage martensitic transformation in the NiTi alloys preceded by the Rphase transition my be induced by: low temperature annealing of the deformed alloy, thermal cycling and precipitation caused by ageing, The TEM observations of samples with two stage transformation have shown that the 'dislocations are distributed inhomogeneously and form a small-angle subgrain boundaries. The Granato-Lucke analysis.of the internal friction peaks related to the two-stage transformation confirmed the difference in dislocation density released in both stages. Thus the two stage martensitic transformation is caused by the inhomogenity in the stress field which results from the dislocation configuration during the praious mentioned processes.
Applied Physics A, 2018
Martensitic transformations are diffusionless shear transformations. The transformation is usually driven by mechanical deformation or by a change in temperature. This study investigated morphological and crystallographic properties of thermally and deformation-induced austenite-martensite phase transformations in the Fe-31.5Ni-10Mn (wt%) alloy. Microstructural characterization was carried out by using a transmission electron microscope (TEM). It was seen that austenite-martensite phase transformation was → ′ (fcc→bcc) and the morphology of martensite was lath type. It was also determined that the habit plane of martensite was (2 5 9) and the orientation relationship between the main and product crystal structures was Kurdjumov-Sachs type. The dilatation parameter of martensite was calculated to be � ≅ 0.91. Accordingly, it was found that martensitic phase transformations in the Fe-31.5Ni-10Mn alloy had the isothermal kinetics. Moreover, it was revealed that thermally and deformation-induced martensitic transformations had similar characteristics in terms of morphological and crystallographic aspects.
Formation and reversion of strain induced martensite on Fe-Cr-Ni alloys
Rem: Revista Escola de Minas, 2013
Austenitic stainless steels represent a significant portion of the alloys used in the aeronautical, chemical, shipbuilding, food processing and biomechanical industries. They combine good mechanical properties with high corrosion resistance. When subjected to cold deformation, these steels exhibit a metastable phase called: strain induced martensite (ferromagnetic), whose formation increases mechanical strength and formability, allowing for a wide range of applications. Heated from room temperature, the strain induced martensite transforms to austenite (non-magnetic). It is easy to find information in literature about the strain induced martensite for 18Cr/8Ni austenitic steels, but there is no data for high nickel alloys like A286 (26Ni, 15Cr), Incoloy 800 (30-40 Ni, 21Cr) and Inconel (50Ni, 19Cr). Therefore, this study aimed to verify the formation of strain induced martensite after cold working in Fe-18Cr base alloys with the addition of up to 60 %Ni. The reversion of this phase ...