The Ti-Mn system revisited: experimental investigation and thermodynamic modelling

Autor(en)
A. U. Khan, P. Broz, M. Premovic, J. Pavlu, J. Vrestal, X. Yan, D. Maccio, A. Saccone, G. Giester, P. Rogl
Abstrakt

As the Ti-Mn phase diagram is part of numerous ternary and higher order systems of technological importance, the present paper defines phase relations which have been experimentally established throughout this work from 800 °C to the melting range based on Differential Thermal Analyses (DTA), X-ray powder diffraction, metallography and Electron Probe Micro Analysis (EPMA) techniques on ∼50 alloys, which were prepared by arc melting or high frequency melting under high purity argon starting from freshly cleaned metal ingots. Novel compounds were identified and reaction isotherms were redefined accordingly. In the Ti-rich region a novel compound TiMn was detected, sandwiched between the known phases: TiMn

1-x (∼45 at% Mn) and TiMn

1+x (∼55 at% Mn). In the Mn-rich region the hitherto unknown crystal structure of TiMn

∼3 was solved from X-ray single crystal diffraction data and found to be of a unique structure type Ti

6(Ti

1-xMn

x)

6Mn

25 (x = 0.462; space group Pbam (#55); a = 0.79081(3) nm, b = 2.58557(9) nm, c = 0.47931(2) nm), which consists of two consecutive layers of the hexagonal MgZn

2-type Laves phase (TiMn

2) and a combined layer of alternate structure blocks of MgZn

2 type and Zr

4Al

3 type. Whereas TiMn can be considered as a line compound (solubility range <∼1 at%), the homogeneity regions of the Ti-Mn compounds are significant (determined by EPMA): TiMn

1-x (44.0 to 46.6 at% Mn), TiMn

1+x (54.6 to 56.3 at% Mn), Ti

1+xMn

2-x (MgZn

2-type, 59 to 69 at% Mn at 1000 °C: -0.08 < x < 0.23), TiMn

∼3 (unique type; 74 to 76.5 at% Mn) and TiMn

∼4 (R-phase: Ti

8(Ti

xMn

1-x)

6Mn

39, 80 to 84 at% Ti). Supported by ab initio calculations of the ground state energy for the Laves phase, the new experimental results enabled thermodynamic modelling of the entire Ti-Mn phase diagram providing a complete and novel set of thermodynamic data thus providing a sound basis for future thermodynamic predictions of higher order Ti-Mn-X-Y systems.

Organisation(en)
Institut für Physikalische Chemie, Institut für Mineralogie und Kristallographie, Institut für Materialchemie
Externe Organisation(en)
Rutgers University, Masaryk University, University of Prishtina, Università degli Studi di Genova, Technische Universität Wien
Journal
Physical Chemistry Chemical Physics
Band
18
Seiten
23326-23339
Anzahl der Seiten
14
ISSN
1463-9076
DOI
https://doi.org/10.1039/c6cp04542a
Publikationsdatum
09-2016
Peer-reviewed
Ja
ÖFOS 2012
104017 Physikalische Chemie, 105113 Kristallographie, 103006 Chemische Physik
Schlagwörter
ASJC Scopus Sachgebiete
Allgemeine Physik und Astronomie, Physical and Theoretical Chemistry
Link zum Portal
https://ucrisportal.univie.ac.at/de/publications/f34c5adb-0383-40b3-b04c-5ba0316fde85