Investigation of Microstructure Development During α-γ-α Phase Transformation in Steel by Using High Temperature in situ EBSD

A newly developed laser powered heating stage for commercial SEMs in combination with automated established electron backscatter diffraction (EBSD) data acquisition is presented. This novel experimental setup can be used to achieve more information about microstructure and orientation changes during grain growth, recrystallization, recovery, and phase transformations. First results on the α−γ−α phase transformation in steel within 886∘C–900∘C are presented.

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Property Improvement of Additively Manufactured Ti64 by Heat Treatment Characterized by In Situ High Temperature EBSD and Neutron Diffraction

Metals ◽

10.3390/met11101661 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1661

Author(s):

Shigehiro Takajo ◽

Toshiro Tomida ◽

El’ad N. Caspi ◽

Asaf Pesach ◽

Eitan Tiferet ◽

...

Keyword(s):

Heat Treatment ◽

Phase Transformation ◽

High Temperature ◽

Grain Boundaries ◽

Beta Phase ◽

Powder Materials ◽

Layer By Layer ◽

Slow Cooling ◽

Α Phase

Among various off-equilibrium microstructures of additively manufactured Ti-6Al-4V alloy, electron beam powder bed fusion, in which three dimensional metallic objects are fabricated by melting the ingredient powder materials layer by layer on a pre-heated bed, results in a specimen that is nearly free of the preferred orientation of the α-Ti phase as well as a low beta phase fraction of ∼1 wt%. However, when further heat treatment of up to 1050 ∘C was applied to the material in our previous study, a strong texture aligning the hexagonal basal plane of α phase with the build direction and about 6% β phase appeared at room temperature. In this study, to understand the mechanism of this heat treatment, the grain level microstructure of the additively manufactured Ti-6Al-4V was investigated using in situ high temperature EBSD up to 1000 ∘C, which allows the tracking of individual grains during a heat cycle. As a result, we found a random texture originating from the fine grains in the initial material and observed a significant suppression of α phase nucleation in the slow cooling after heating to 950 ∘C within the α and β dual phase regime but close to the the β-transus temperature at ∼980 ∘C, which led to a coarse microstructure. Furthermore, the texture resulting from phase transformation of the additively manufactured Ti-6Al-4V assuming nucleation at the grain boundaries was modeled, using the double Burgers orientation relationship for the first time. The model successfully reproduced the measured texture, suggesting that the texture enhancement of the α phase by the additional heat treatment derives also from the variant selection during the phase transformation and nucleation on grain boundaries.

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Analyses of Eutectoid Phase Transformations in Nb–SilicideIn SituComposites

Microscopy and Microanalysis ◽

10.1017/s1431927604040760 ◽

2004 ◽

Vol 10 (4) ◽

pp. 470-480 ◽

Cited By ~ 17

Author(s):

B.P. Bewlay ◽

S.D. Sitzman ◽

L.N. Brewer ◽

M.R. Jackson

Keyword(s):

Crystal Structure ◽

Phase Transformation ◽

High Temperature ◽

Room Temperature ◽

Bulk Composition ◽

High Strength ◽

Eutectoid Decomposition ◽

Quaternary Alloys ◽

Temperature Fracture

Nb–silicide in situ composites have great potential for high-temperature turbine applications. Nb–silicide composites consist of a ductile Nb-based solid solution together with high-strength silicides, such as Nb5Si3and Nb3Si. With the appropriate addition of alloying elements, such as Ti, Hf, Cr, and Al, it is possible to achieve a promising balance of room-temperature fracture toughness, high-temperature creep performance, and oxidation resistance. In Nb–silicide composites generated from metal-rich binary Nb-Si alloys, Nb3Si is unstable and experiences eutectoid decomposition to Nb and Nb5Si3. At high Ti concentrations, Nb3Si is stabilized to room temperature, and the eutectoid decomposition is suppressed. However, the effect of both Ti and Hf additions in quaternary alloys has not been investigated previously. The present article describes the discovery of a low-temperature eutectoid phase transformation during which (Nb)3Si decomposes into (Nb) and (Nb)5Si3, where the (Nb)5Si3possesses the hP16 crystal structure, as opposed to the tI32 crystal structure observed in binary Nb5Si3. The Ti and Hf concentrations were adjusted over the ranges of 21 to 33 (at.%) and 7.5 to 33 (at.%) to understand the effect of bulk composition on the phases present and the eutectoid phase transformation.

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In Situ Isothermal High-Temperature Diffraction Studies on the Crystallization, Phase Transformation, and Activation Energies in Anodized Titania Nanotubes

Nanostructured Titanium Dioxide in Photocatalysis ◽

10.1201/9781003148531-7 ◽

2021 ◽

pp. 115-125

Author(s):

It-Meng Low ◽

Hani Manssor Albetran ◽

Victor Manuel de la Prida Pidal ◽

Fong Kwong Yam

Keyword(s):

Phase Transformation ◽

High Temperature ◽

Activation Energies ◽

Titania Nanotubes

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2.45 GHz Microwave Sintering of Silicon Nitride

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.403.27 ◽

2008 ◽

Vol 403 ◽

pp. 27-30

Author(s):

S. Chockalingam ◽

J.P. Kelly ◽

V.R.W. Amarakoon ◽

James R. Varner

Keyword(s):

Phase Transformation ◽

Oxidation Behavior ◽

Microwave Sintering ◽

Sintered Sample ◽

Microstructure Development ◽

X Ray Diffraction ◽

X Ray ◽

Β Phase ◽

Structurally Stable

Microwave sintered Si3N4-MgO system that contains 2, 4 and 10 wt% of ZrO2 as secondary particulates were investigated with respect to phase transformation and microstructure development. The experimental results of microwave sintered samples were compared with conventional methods. Complete α to β phase transformation was observed in the case of microwave sintered samples due to the volumetric nature of microwave heating. High temperature X-ray diffraction (HTXRD) analysis was performed to study in-situ the oxidation behavior of Si3N4 specimens. Si3N4 specimens with 10 wt % ZrO2 were exposed to air at temperature between 25°C and 900°C for up to 24 hours. Microwave sintered sample were structurally stable in air 25°C and 900°C for up to 24 hours of testing.

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In Situ Investigation of a High Temperature Phase Transformation Using Laser Heating and Synchrotron Diffraction

ECS Meeting Abstracts ◽

10.1149/ma2012-02/24/2330 ◽

2012 ◽

Keyword(s):

Phase Transformation ◽

High Temperature ◽

Laser Heating ◽

High Temperature Phase ◽

Temperature Phase ◽

Synchrotron Diffraction ◽

In Situ Investigation

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

Crystals ◽

10.3390/cryst8090360 ◽

2018 ◽

Vol 8 (9) ◽

pp. 360 ◽

Cited By ~ 6

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.

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