The effect of deformation treatment on the decomposition of supersaturated Ni(Nb,B) and Ni(Mo,B) solid solutions synthesized by mechanical alloying

The effect of rotary-shear deformation during powders compacting on the decomposition of supersaturated Ni(Nb,B) and Ni(Mo,B) solid solutions is studied. The metastable fcc solid solutions were synthesized by mechanical alloying (MA) of the mixtures of components of Ni75Nb12B13 and Ni73Mo14B13 compositions. The powders were compacted on a Bridgman anvil. Col plastic deformation action is realized by using this technique. As a result the initial structure of nonequilibrium supersaturated solid solutions changed.The data of X-ray diffraction analysis and scanning electron microscopy showed a partial decomposition of Ni(Nb,B) and Ni(Mo,B) solid solutions, which leads to the formation of cubic boride τ phases – Ni21Nb2B6 with a lattice parameter of а = 1.0572 nm and, correspondingly, Ni21Mo2B6 phase with a lattice parameter of а = 1.0498 nm. The τ phase probably forms coherently to the fcc crystal lattice of solid solution because of its lattice parameter is equal to three lattice parameter of nickel. According to the data of local X-ray spectral analysis, the compacted alloys are heterogeneous and are contained boron-reach and also niobium- and molybdenum-rich regions.

• Influence of deformation on decomposition of Ni-based solid solutions was studied. • X-ray diffraction analysis and scanning electron microscopy were used. • Decomposition of Ni(Nb,B), Ni(Mo,B) solid solutions takes place under deformation. • Formation of Ni21(Nb,Mo)2B6τ-phases after deformation treatment is observed. • Identity of MA and deformation on the decomposition of solid solutions is shown.