Phase transformations in Ti2Cu under destructive hydrogenation and recombination

Abstract

The thermodynamic possibility and conditions of Ti 2 Cu hydrogenation and recombination are assessed. The mechanism of Ti 2 Cu interaction with hydrogen between 293 and 973 K at pressure 1.0 MPa is studied. The interaction of Ti 2 Cu with hydrogen is thermodynamically possible in the destructive hydrogenation region over a wide temperature range. X-ray diffraction shows that destructive hydrogenation products are titanium dihydride and copper-rich intermetallic phases and copper depending on reaction conditions. According to the established mechanism of Ti 2 Cu destructive hydrogenation, hydrogen selectively interacts with titanium leaving Ti 2 Cu composition as follows: β-TiH y (bct-bcc) → TiH 1.92 (fcc). The initial Ti 2 Cu composition is recombined from destructive hydrogenation products (titanium dihydride and copper) in vacuum and hydrogen. The minimum temperature of Ti 2 Cu vacuum recombination is 1050 K and ensures complete TiH 2 decomposition. The recombination of Ti 2 Cu in hydrogen can occur at temperatures above 907 K.Compounds of titanium with copper are promising functional materials with high hardness, electrical and thermal conductivity, and satisfactory sound absorptivity. Coatings based on Ti-Cu intermetallides can greatly improve the sliding surfaces and tribotechnical properties in general. There are six intermetallic compounds known in the Ti-Cu system: Ti 2 Cu, TiCu, Ti 3 Cu 4 , Ti 2 Cu 3 , TiCu 2 , and β-TiCu 4 [1]. This paper considers the interaction of hydrogen with Ti 2 Cu, which has tetragonal crystal lattice of MoSi 2 type (structural group 17 4h D ) with parameters a = 0.2943 nm and c = 1.0784 nm [2].The interaction between Ti 2 Cu and hydrogen was earlier studied in [3][4][5][6][7], but none of the papers provided diffraction patterns of the reaction products. Nevertheless, it is stated in [3,4] that the reaction products are represented by titanium hydride and copper above 473 K and by direct hydride Ti 2 CuH 2.6 below 473 K [5, 6]. Padurets and colleagues [7] obtained TiCuH 2 and TiH 2 by Ti 2 Cu hydrogenation at 293-673 K and hydrogen pressure 0.1 MPa. The isothermal line of Ti 2 Cu-H equilibrium at 773 and 823 K was also studied [4]. Five pressure plateaus associated with heterophase composition of the system that interacts with hydrogen are revealed. Hence,

Basic Electrochemical Behavior of Ti-7Cu Alloys for Medical Applications

“…The lattice parameters of α phase in a Ti Cu binary system were determined to have a hexagonal structure (space group P 63/mmc) with lattice parameters of a = 0.2945 nm and c = 0.4685 nm. Also, the crystallographic characteristics of Ti 2 Cu compound are well de ned in the literature as a tetragonal structure (space group I4/mmm) with lattice parameters of a = 0.29438 nm and c = 1.0786 nm [20]. It was found that the X-ray di raction patterns of as-cast samples showed both α ′ martensite and α-Ti phases and slight peaks associated with the intermetallic Ti 2 Cu, as observed in Fig.…”

Formation of ultrafine structure in as cast Ti7CuXSn alloys

“…Regardless of the cooling rate applied, such precipitation is unavoidable. 20 Williams et al 13 reported that the supersaturated a9-martensite structure was precipitated in alloys containing up to 6 wt-%Cu during aging. The high cooling rate imposed on the samples promoted complete b phase decomposition and the formation of the acicular plates of martensite typically found in titanium alloys.…”

“…The microstructure of the as cast samples (in a copper mould) is in good agreement with the previously reported results. 13,14,20 In general, the fully lamellar microstructure consists of equiaxed polycrystalline grains and lamellae within the grains in the Ti alloys as show in Fig. 6.…”

“…In addition, the crystallographic characteristics of Ti 2 Cu phase are well defined in the literature as a tetragonal structure (space group I4/mmm) with lattice parameters of a50?29438 nm and c51?0786 nm. 20 In order to clarify the formation of a9-Ti and a-Ti phase in these alloys, high resolution XRD was carried out. Figure . 7b was scanned from 2h533u to 2h555u.…”

Thermodynamic analysis of the formation and decomposition of intermetallic hydrides

“…We previously examined [7,8] the mechanism of destructive hydrogenation of Ti 3 Al and Ti 2 Cu involving the decomposition of starting intermetallides because of the selective hydrogenation of titanium in certain thermodynamic conditions. It was established that new titanium-depleted intermetallic phases formed when titanium left the starting intermetallide.…”