In situ Observation of Phase Transformation in MnAl(C) Magnetic Materials

Metastable β-Ti alloys exhibit various solid-solid phase transitions. Our study is focused on the characterization of the diffusion controlled β→ωiso phase transition. The particles of ω phase play an important part in thermomechanical treatment since they serve as heterogeneous nucleation sites for precipitation of finely dispersed particles of hexagonal α phase. The in-situ observation of the growth of particles of ω phase could be difficult by conventional techniques. However, it was shown recently that the ω phase significantly influences the elastic constants of the material, and the different forms of ω phase have different effects on the elastic anisotropy, as well as on the internal friction coefficients. Therefore, the β→ω phase transformation could be in-situ observed by the precise measurement of the tensor of elastic constants. In this contribution, we present the study of the kinetics of the β→ωiso phase transformation by resonant ultrasound spectroscopy. The polycrystalline samples of TIMETAL LCB alloy were in-situ examined by this technique during isothermal and non-isothermal ageing at temperatures up to 300 °C.

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In situ observation of phase transformation in an Fe–Zn system at high temperatures using an image plate

Journal of Synchrotron Radiation ◽

10.1107/s0909049597017640 ◽

1998 ◽

Vol 5 (3) ◽

pp. 983-985 ◽

Cited By ~ 4

Author(s):

Masao Kimura ◽

Muneyuki Imafuku ◽

Masao Kurosaki ◽

Siro Fujii

Keyword(s):

Phase Transformation ◽

High Temperatures ◽

Heating System ◽

Crystallographic Structure ◽

In Situ Observation ◽

Image Plate ◽

Unique System ◽

Different Types ◽

Diffraction Patterns

A unique system has been developed for in situ observation of phase transformation at high temperatures. Changes in powder-diffraction patterns from a heated specimen can be measured continuously by scanning an image plate located behind a slit. A heating system has been designed for a sheet specimen (∼5 × 6 mm) using Joule heating, and it can heat the specimen up to 1100 K at a rate of up to 160 K s−1, where effects of thermal expansion are minimized by a mechanism releasing stress. This system was applied to Zn-coated (∼8 µm in thickness) steel. At temperatures higher than the melting point of Zn, different types of Fe–Zn intermetallics formed sequentially through rapid interdiffusion. Changes in phase and crystallographic structure were monitored with a time resolution of less than a few seconds. It has been found that an addition of a small amount of an element, such as P, into Fe changes the incubation time before the alloying reaction starts. This system has been shown to have the potential for application to in situ observation of other reactions at high temperatures.

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In-situ observation of phase transformation in amorphous silicon during Joule-heating induced crystallization process

Thin Solid Films ◽

10.1016/j.tsf.2011.03.053 ◽

2011 ◽

Vol 519 (16) ◽

pp. 5516-5522 ◽

Cited By ~ 11

Author(s):

Dong-Hyun Kim ◽

Won-Eui Hong ◽

Jae-Sang Ro ◽

Seong Hyuk Lee ◽

Chang-Hoon Lee ◽

...

Keyword(s):

Phase Transformation ◽

Amorphous Silicon ◽

Joule Heating ◽

Crystallization Process ◽

In Situ Observation ◽

Induced Crystallization

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In situ TEM study of irradiation-induced transformation in TiNi shape memory alloys

MRS Proceedings ◽

10.1557/proc-792-r1.10 ◽

2003 ◽

Vol 792 ◽

Author(s):

X. T. Zu ◽

F.R. Wan ◽

S. Zhu ◽

L. M. Wang

Keyword(s):

Phase Transformation ◽

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Electron Irradiation ◽

Room Temperature ◽

Critical Voltage ◽

In Situ Tem ◽

In Situ Observation

ABSTRACTTiNi shape memory alloy (SMA) has potential applications for nuclear reactors and its phase stability under irradiation is becoming an important topic. Some irradiation-induced diffusion-dependent phase transformations, such as amorphization, have been reported before. In the present work, the behavior of diffusion-independent phase transformation in TiNi SMA was studied by electron irradiation at room temperature. The effect of irradiation on the martensitic transformation of TiNi shape memory alloys was studied by Transmission Electron Microscopy (TEM) with in-situ observation and differential scanning calorimeter (DSC). The results of TEM and DSC measurements show that the microstructure of samples is R phase at room temperature. Electron irradiations were carried out using several different TEM with accelerating voltage of 200 kV, 300 kV, 400 kV and 1000 kV. Also the accelerating voltage in the same TEM was changed to investigate the critical voltage for the effect of irradiation on phase transformation. It was found that a phase transformation occurred under electron irradiation above 320 kV, but never appeared at 300 kV or lower accelerating voltage. Such phase transformation took place in a few seconds of irradiation and was independent of atom diffusion. The mechanism of Electron-irradiation-induced the martensitic transformation due to displacements of atoms from their lattice sites produced by the accelerated electrons.

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