Reduction of thermal expansion anisotropy for intermetallic silicides of 16H crystal structure

Controlling the thermal expansion anisotropy of Mo5Si3 and Ti5Si3 silicides

“…Ikarashi et al [11] found indeed that alloying with Zr (which is larger than Ti) reduces the thermal expansion anisotropy of Ti 5 Si 3 significantly. However, since their CTE(c)/CTE(a) value for binary Ti 5 Si 3 is unusually low there is some question about the accuracy of their data.…”

“…Preparation of Ti 5 Si 3 by powder-metallurgical methods may therefore result in different CTE anisotropy values than preparation by arccasting. Also, whereas Williams et al used, as we did, fullpattern refinement to determine the lattice parameters, Ikarashi et al [11] and Zhang and Wu [12] did not. Zhang et al used a Rigaku Dmax IIIA diffractometer equipped with a Pt alloy heater.…”

Thermal expansion of the Ti5Si3 and Ti6Si2B phases investigated by high-temperature X-ray diffraction

“…In another work, Schneibel et al shown that the thermal expansion anisotropy of Ti 5 Si 3 phase can be reduced from 2.7 to 2.5 with 2 at% of Cr addition [19]. However, some discrepancies in the a c /a a ratio of this phase have been reported by different authors: 2.8 [20]; 2.4 [21]; 1.7 [22] and 4.4 [23]. The Ti 6 Si 2 B phase, recently identified by Ramos et al [24], is isotypic with Ni 6 Si 2 B (Fe 2 P-type structure; Zr 6 CoGa 2 ternary variant), hexagonal structure, lattice parameters aZ6.8015 Å and cZ3.3377 Å , space group P62m, Wyckoff positions: Ti 1 Z3 g (X Ti1 , 0, 1/2), where X Ti1 Z0.2418; Ti 2 Z3f (X Ti2 , 0, 0) where X Ti2 Z0.5996; BZ1a (0, 0, 0) and SiZ2d (1/3, 2/3, 1/2) [24].…”

Niobium addition enhancing the corrosion resistance of nanocrystalline Ti5Si3 coating in H2SO4 solution

“…For example, Thom et al [17] suggested that a critical grain size of pure Ti 5 Si 3 and carbon-containing Ti 5 Si 3 is 2-3 lm and 5-6 lm, respectively, needed to completely avoid microcracking. Experimental observations also indicated that the thermal-expansion anisotropy of Ti 5 Si 3 exhibits a substantial reduction by replacing some of the titanium by zirconium, niobium or chromium [18,19]. It is worth noting that previous studies focused mainly on physical and mechanical properties, with little attention devoted to understanding the electrochemical behavior of Ti 5 Si 3 in aqueous corrosive environments.…”