Hydrogen pulverization of refractory metals, alloys and intermetallics

Hydrogen-induced pulverization allows the production of fine powders with high purity and low cost in refractory metals, alloys, and intermetallics. In this paper, their hydrogen pulverization behavior has been investigated in order to further utilize hydrogen pulverization as a new powder fabrication process. Hydrogen pulverization was examined by the following three methods: (i) hydrogenation in an arc-melting chamber for NbCr₂ and Ta ₂Ni alloys; (ii) measurement of hydrogen absorption-desorption curves in a Sieverts-type apparatus for Nb₃Al alloys; and (iii) heat treatment in a hydrogen furnace for pure Ta. Two-phase alloys of NbCr ₂/Nb_ss, Nb₃Al/Nb_ss, Nb ₃Al/Nb₂Al, Ta₂Ni/Ta_ss and Ta _ss/Ta₂H (Nb_ss and Ta_ss denote Nb and Ta solid solutions, respectively) are pulverized by absorbing a large amount of hydrogen. It is suggested that cracking leading to pulverization is initiated at brittle intermetallic regions or hydrides, which are fractured by lattice expansion of Nb_ss or Ta_ss due to hydrogen absorption.