Issue 33, 2016

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

Abstract

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: TiMn1−x (∼45 at% Mn) and TiMn1+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 Ti6(Ti1−xMnx)6Mn25 (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 MgZn2-type Laves phase (TiMn2) and a combined layer of alternate structure blocks of MgZn2 type and Zr4Al3 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): TiMn1−x (44.0 to 46.6 at% Mn), TiMn1+x (54.6 to 56.3 at% Mn), Ti1+xMn2−x (MgZn2-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: Ti8(TixMn1−x)6Mn39, 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.

Graphical abstract: The Ti–Mn system revisited: experimental investigation and thermodynamic modelling

Supplementary files

Article information

Article type
Paper
Submitted
29 Jun 2016
Accepted
23 Jul 2016
First published
26 Jul 2016

Phys. Chem. Chem. Phys., 2016,18, 23326-23339

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

A. U. Khan, P. Brož, M. Premović, J. Pavlů, J. Vřeštál, X. Yan, D. Maccio, A. Saccone, G. Giester and P. Rogl, Phys. Chem. Chem. Phys., 2016, 18, 23326 DOI: 10.1039/C6CP04542A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements