Preparation of nanocrystalline Nb₃Al powders by mechanical grinding and alloying

Nanocrystalline Nb₃Al powders were prepared by hydrogen-plasma arc melting followed by mechanical grinding of hydrogen-disintegrated powders. They could be dehydrogenated at and above 873 K to yield a pure Nb₃Al intermetallic compound with an apparent activation energy for dehydrogenation of 170 kJ/mol. Mechanical grinding of as-disintegrated powders for 180 ks produced Nb₃Al containing a very small amount of hydrogen but their crystallite sizes were about 5 nm. On the other hand, mechanical alloying of elemental Nb and Al powders for 180 ks produced a homogeneous mixture of nanocrystalline Nb₃Al of about 5 nm with a small amount of unreacted Nb. The apparent activation energy for forming Nb₃Al is 240 kJ/mol. Annealing of MG and MA powders in a temperature range of 873 to 1073 K indicates that only a very slight grain growth occurs.