title: 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.
authors: Institute of Materials Chemistry and Research, University of Vienna, Währingerstraße 42, A-1090 Vienna, Austria. peter.franz.rogl@univie.ac.at.
authors: A U
authors: AU
authors: Khan
authors: Masaryk University, Faculty of Science, Department of Chemistry, Kotlářská 2, 611 37, Brno, Czech Republic and Masaryk University, Central European Institute of Technology, CEITEC, Kamenice 753/5, 62500, Brno, Czech Republic.
authors: P
authors: P
authors: Brož
authors: Masaryk University, Faculty of Science, Department of Chemistry, Kotlářská 2, 611 37, Brno, Czech Republic.
authors: M
authors: M
authors: Premović
authors: Masaryk University, Faculty of Science, Department of Chemistry, Kotlářská 2, 611 37, Brno, Czech Republic and Masaryk University, Central European Institute of Technology, CEITEC, Kamenice 753/5, 62500, Brno, Czech Republic.
authors: J
authors: J
authors: Pavlů
authors: Masaryk University, Faculty of Science, Department of Chemistry, Kotlářská 2, 611 37, Brno, Czech Republic and Masaryk University, Central European Institute of Technology, CEITEC, Kamenice 753/5, 62500, Brno, Czech Republic.
authors: J
authors: J
authors: Vřeštál
authors: Institute of Materials Chemistry and Research, University of Vienna, Währingerstraße 42, A-1090 Vienna, Austria. peter.franz.rogl@univie.ac.at.
authors: X
authors: X
authors: Yan
authors: Dipartimento di Chimica e Chimica Industriale, Università di Genova, Sezione di Chimica Inorganica e Metallurgica, Via Dodecaneso 31, I-16146 Genova, Italy.
authors: D
authors: D
authors: Maccio
authors: Dipartimento di Chimica e Chimica Industriale, Università di Genova, Sezione di Chimica Inorganica e Metallurgica, Via Dodecaneso 31, I-16146 Genova, Italy.
authors: A
authors: A
authors: Saccone
authors: Institute of Mineralogy and Crystallography, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria.
authors: G
authors: G
authors: Giester
authors: Institute of Materials Chemistry and Research, University of Vienna, Währingerstraße 42, A-1090 Vienna, Austria. peter.franz.rogl@univie.ac.at and Christian Doppler Laboratory for Thermoelectricity, Vienna, Austria.
authors: P
authors: P
authors: Rogl