Mechanical and Reactive Milling of a TiCrV BCC Solid Solution

Abstract

Nowadays, many efforts have been concentrated in research and development of hydrogen absorbing materials due to a possible application as electrode for rechargeable batteries, on board hydrogen storage systems, getters, catalysts, etc. Novel technologies for materials processing have been used to generate new alloys with metastable structures, such as amorphous and/or nanocrystalline alloys. In this context, mechanical milling or mechanical alloying is a very attractive way to produce this alloys, specially when carried out under hydrogen atmosphere (reactive milling). In this work, we have studied the structural evolution of a TiCrV bcc solid solution during mechanical and reactive milling. The process parameters analyzed were: milling atmosphere (argon and hydrogen), milling time and gas pressure into the vials (in the case of reactive milling). Structural evolution was investigated by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM). Hydrogen contents of the reactive milled alloys were determined using a Leco analyzer. Differential scanning calorimetry (DSC) was used to determine the hydrogen desorption temperature and the stability of the alloys.

Mg-based Nanocomposites for Hydrogen Storage Containing Ti-Cr-V Alloys as Additives

“…However, for some areas, the Ti seems to be in high concentration in comparison to the others, indicating that the additive could probably decompose during milling. This was already reported by Santos 25 during the reactive milling of BCC alloys. Figure 3 for the onset temperatures, both additives used were effective in the reduction of desorption temperature ranges.…”

“…But when TiCrV alloys are prepared by RM, lower desorption temperatures are observed 25 . Figure 6(a) to 6(c).The mapping reveals that the agglomerate region is partially composed by additive particles Ti, Cr and V which appears brighter in their respective maps, beyond Mg (not mapped, but can be understood as the dark regions in each map).…”

Processing and microstructural characterization of a Ti-Cr-Nb alloy synthesized by high-energy ball-milling

“…The substantial increase on Fe contamination can be explained by the fast formation of the BCC solid solution, observed on the XRD patterns. This BCC phase is very hard when compared to the pure metallic elements, thus leading to an excessive wear of the milling balls and vial, as previously commented 9 . Concerning the chemical homogeneity of the samples, Figures 3 and 4 show the compositional maps (EDX mapping) for the alloying elements and iron after 2 and 8 hours of milling, respectively.…”

“…Conversely, a remaining peak of Cr is detectable in all diffraction patterns which suggest a slower incorporation of this element which has the smallest atomic volume or contamination with Fe. For short milling time, it is unlikely a significant contamination with Fe but for longer milling times the abrasive wear promoted by hard BCC phase particles can lead to a extensive contamination with Fe, as observed for high energy ball-milling of a Ti-Cr-V cast alloy 9 . Figure 2 shows the scanning electron microscopy image in secondary electron mode (SEM-SE) of the alloy milled by 8 hours.…”

Nanocrystalline Metal Hydrides Obtained by Severe Plastic Deformations

“…In the case of BCC phase the reason may be reduction of lattice parameters. Iron contamination (even at this low level) may also play a role as shown by Santos et al in Ti-V-Cr system [46].…”