Microstructure and First Hydrogenation Properties of Ti30V60Mn(10−x)Crx (x = 0, 3.3, 6.6, 10) + 4 wt.% Zr

Abstract

In this paper, we studied the effect of the Cr/Mn ratio on the microstructure, crystal structure and hydrogen absorption properties of the quaternary alloys of compositions Ti30V60Mn(10−x)Crx (x = 0, 3.3, 6.6 and 10) + 4 wt.% Zr. The addition of Hf instead of Zr was also investigated. We found that all alloys are single-phase BCC (Body Centred Cubic) but with regions of high concentration of Zr (or Hf). The first hydrogenation at room temperature under 2 MPa of hydrogen happens quickly without any incubation time. The Ti30V60Mn3.3Cr6.6 + 4 wt.% Zr alloy showed the fastest kinetics and highest hydrogen absorption (3.8 wt.%). For this composition, replacing Zr with Hf made the first hydrogenation slower and reduced the capacity to 3.4 wt.%. No activation was observed for the same alloy without additives. As the alloy without additives did not absorb hydrogen at all, it means that the presence of these high concentrations of Zr (or Hf) is essential for quick first hydrogenation.