Phase Evolution During High-Energy Ball Milling and Annealing of Ti-Doped Mo-V-Si-B Alloys

Refractory metal-based Mo-Si-B alloys have long been considered the most
promising candidates for replacing nickel-based superalloys in the aerospace and energy
sector due to their outstanding mechanical properties and good oxidation of the Mo-silicide
phases. In general, the addition of vanadium to Mo-Si-B alloys leads to a significant density
reduction, while small amounts of titanium provide additional strengthening without
changing the phase evolution within the Moss-Mo$_3$Si-Mo$_5$SiB$_2$ phase field. In this work,
high-energy ball milling studies on Mo-40V-9Si-8B, substituting both molybdenum and
vanadium with 2 and 5 at. % Ti in all constituents, were performed to evaluate the potential
milling parameters and investigate the effects of Ti doping on the milling characteristics
and phase formation of these multicomponent alloys. After different milling durations,
the powders were analysed with regard to their microstructure, particle size, oxygen
concentration and microhardness. After heat treatment, the silicide phases (Mo,V)$_3$Si and
(Mo,V)$_5$SiB$_2$ precipitated homogeneously within a (Mo,V) solid solution matrix phase.
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Thermodynamic phase calculations using the CALPHAD method showed good agreement
with the experimental phase compositions after annealing, confirming the stability of the
observed microstructure.