Synthesis of Ti–5Al–2.5Fe Alloy and Its Hydride by HC and SHS Methods

Abstract

The aim of this investigation was to synthesis Ti–5Al–2.5Fe alloy by “hydride cycle” (HC) method. The crystal structure of obtained alloy was studied by powder X-ray diffraction. It was found that the alloy was a near α-alloy containing main α phase (hexagonal close-packed structure, space group 194: P6₃/mmc) and small amount of β phase (body-centered cubic structure, space group 229: Im-3m). The microstructure of obtained materials was studied using scanning electron microscope (SEM) in a back-scattered electron (BSE) mode. On the SEM image of the synthesized compacted alloy no cracks and pores were observed. The SEM measurements showed that the particles synthesized hydride have size distribution in the range of 1–10 μm. Energy dispersive X-ray spectrometry (EDS) analysis showed that the chemical compositions of observed main grey phase were close to the nominal composition of Ti–5Al–2.5Fe α-phase. The hydride of Ti–5Al–2.5Fe alloy was synthesized by self-propagating high temperature synthesis (SHS) method. It was shown that Ti–5Al–2.5Fe tablets reacted with hydrogen without preliminary crushing in SHS mode at range of hydrogen pressure P(H₂) = 1–2.5 MPa. Hydrogen capacity of synthesized (Ti–5Al–2.5Fe)H_1.45 hydride was equal to 3.04 wt %. The density of synthesized alloy before (ρ₁ = 4.0487 g/cm³) and after (ρ₂ = 4.2511 g/cm³) the repeating of hydrogenation–dehydrogenation cycle was measured. It was found that as a result of cycle the density of sample was increased by 5%.