scholarly journals Mechanism of the Intermediary Phase Formation in Ti-20 wt. % Al Mixture during Pressureless Reactive Sintering

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2171 ◽  
Author(s):  
Andrea Školáková ◽  
Pavel Salvetr ◽  
Pavel Novák ◽  
Jindřich Leitner ◽  
Davy Deduytsche

This work aims to describe the mechanism of intermediary phases formation in TiAl20 (wt. %) alloy composition during reactive sintering. The reaction between titanium and aluminum powders was studied by in situ diffraction and the results were confirmed by annealing at various temperatures. It was found that the Ti2Al5 phase formed preferentially and its formation was detected at 400 °C. So far, this phase has never been found in this alloy composition during reactive sintering processes. Subsequently, the Ti2Al5 phase reacted with the titanium, and the formation of the major phase, Ti3Al, was accompanied by the minor phase, TiAl. Equations of the proposed reactions are presented in this paper and their thermodynamic and kinetic feasibility are supported by Gibbs energies of reaction and reaction enthalpies.

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 189 ◽  
Author(s):  
Francisco García-Moreno ◽  
Laurenz Alexander Radtke ◽  
Tillmann Robert Neu ◽  
Paul Hans Kamm ◽  
Manuela Klaus ◽  
...  

The foaming behaviour of aluminium alloys processed by the powder compaction technique depends crucially on the exact alloy composition. The AlSi8Mg4 alloy has been in use for a decade now, and it has been claimed that this composition lies in an “island of good foaming”. We investigated the reasons for this by systematically studying alloys around this composition by varying the Mg and Si content by a few percent. We applied in situ X-ray 2D and 3D imaging experiments combined with a quantitative nucleation number and expansion analysis, X-ray tomography of solid foams to assess the pore structure and pore size distribution, and in situ diffraction experiments to quantify the melt fraction at any moment. We found a correlation between melt fraction and expansion height and verified that the “island of good foaming” actually exists, and foams outside a preferred range for the liquid fraction—just above TS and between 40–60%—show a poorer expansion performance than the reference alloy AlSi8Mg4. A very slight increase of Si and decrease of Mg content might further improve this foam.


2019 ◽  
Vol 9 (7) ◽  
pp. 1310 ◽  
Author(s):  
Kerstin Hauke ◽  
Johannes Kehren ◽  
Nadine Böhme ◽  
Sinje Zimmer ◽  
Thorsten Geisler

In the last decades, Raman spectroscopy has become an important tool to identify and investigate minerals, gases, glasses, and organic material at room temperature. In combination with high-temperature and high-pressure devices, however, the in situ investigation of mineral transformation reactions and their kinetics is nowadays also possible. Here, we present a novel approach to in situ studies for the sintering process of silicate ceramics by hyperspectral Raman imaging. This imaging technique allows studying high-temperature solid-solid and/or solid-melt reactions spatially and temporally resolved, and opens up new avenues to study and visualize high-temperature sintering processes in multi-component systems. After describing in detail the methodology, the results of three application examples are presented and discussed. These experiments demonstrate the power of hyperspectral Raman imaging for in situ studies of the mechanism(s) of solid-solid or solid-melt reactions at high-temperature with a micrometer-scale resolution as well as to gain kinetic information from the temperature- and time-dependent growth and breakdown of minerals during isothermal or isochronal sintering.


2016 ◽  
Vol 18 (42) ◽  
pp. 29435-29446 ◽  
Author(s):  
Zhuoran Wang ◽  
Samir Elouatik ◽  
George P. Demopoulos

The in situ Raman monitored annealing method is developed in this work to provide real-time information on phase formation and crystallinity evolution of kesterite deposited on a TiO2 mesoscopic scaffold.


2014 ◽  
Vol 70 (a1) ◽  
pp. C500-C500
Author(s):  
Yusuke Yamada ◽  
Naohiro Matsugaki ◽  
Masahiko Hiraki ◽  
Ryuichi Kato ◽  
Toshiya Senda

Crystallization trial is one of the most important but time-consuming steps in macromolecular crystallography. Once a crystal appears in a certain crystallization condition, the crystal is typically harvested from the crystallization drop, soaked into a cryoprotection buffer, flash-cooled with a liquid nitrogen or cold gas flow and finally evaluated its diffraction quality by an X-ray beam. During these long process, crystal may be damaged and the result from the diffraction experiment does not necessarily reflect a nature of the crystal. On in-situ diffraction experiment, where a crystal in a crystallization drop is directly irradiated to an X-ray beam, a diffraction image from a crystal without any external factors such as harvesting and cryoprotection and, as a result, a nature of crystal can be evaluated quickly. In the Photon Factory, a new table-top diffractometer for in-situ diffraction experiments has been developed. It consists of XYZ translation stages with a plate handler, on-axis viewing system with a large numeric aperture and a plate rack where ten crystallization plates can be placed. These components sit on a common plate and it is placed on the existing diffractometer table in the beamline endstation. The CCD detector with a large active area and a pixel array detector with a small active area are used for acquiring diffraction images from crystals. Dedicated control software and user interface were also developed. Since 2014, user operation of the new diffractometer was started and in-situ diffraction experiments were mainly performed for evaluations of crystallization plates from a large crystallization screening project in our facility. BL-17A [1], one of micro-focus beamlines at the Photon Factory, is planned to be upgraded in March 2015. With this upgrade, a new diffractometer, which has a capability to handle a crystallization plate, will be installed so that diffraction data sets from crystals in crystallization drop can be collected.


2021 ◽  
pp. 111695
Author(s):  
Tea-Sung Jun ◽  
Ayan Bhowmik ◽  
Xavier Maeder ◽  
Giorgio Sernicola ◽  
Tommaso Giovannini ◽  
...  

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1637 ◽  
Author(s):  
Domonkos Tolnai ◽  
Tungky Subroto ◽  
Serge Gavras ◽  
Ricardo Buzolin ◽  
Andreas Stark ◽  
...  

Mg-4Nd base alloys with Zn additions of 3, 5 and 8 wt % were investigated with in situ synchrotron radiation diffraction during solidification. This method enabled the investigation of phase formation and transformation in the alloys. The diffraction results were supported with TEM observations on the as-solidified samples. The results show the effect of increased Zn addition on stabilizing the Mg3RE phase (RE—rare earth). The experimental results agree only partially with the theoretical calculations indicating the need to improve the existing thermodynamic database on the alloy system.


2019 ◽  
Vol 39 (4) ◽  
pp. 934-943 ◽  
Author(s):  
Quan Li ◽  
Zhihua Yang ◽  
Jing Zhong ◽  
Yangshan Sun ◽  
Dechang Jia ◽  
...  
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