Mechanochemical Synthesis in the Nb–Al–Si and Nb–Al–Si–C Systemsстатья
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Дата последнего поиска статьи во внешних источниках: 9 июля 2015 г.
Аннотация:Ternary and quaternary alloys of the Nb–Al–Si and Nb–Al–Si–C systems have been produced
by mechanochemical synthesis. Our results demonstrate that the milling of a 62Nb + 19Al + 19Si ternary
mixture, whose composition corresponds to that of the intermetallic phaseNb10Al3Si3, leads to the formation
of an amorphous phase, whereas the milling of a 86Nb + 9Al + 5Si mixture, corresponding to a solid solution,
results in the formation of a twophase mixture, consisting of an amorphous phase and a nanostructured
(7 nm) bcc solid solution. The addition of graphite to the starting mixtures homogenizes the MS products and
reduces their particle size to 2 nm. The milling of a mixture with the composition Nb10Al3Si3C10 causes no
changes in phase composition. The milling of a 78Nb + 8Al + 5Si + 9C mixture leads to the formation of an
additional phase: nanoparticulate niobium carbide. Using differential thermal analysis, we have identified the sequence of transformations underlying the transition of the MS alloys to an equilibrium state. After the compaction of the MS powders by hot isostatic pressing, the samples prepared from the graphitecontaining mix
tures were more homogeneous in the case of both the alloys based on the intermetallic phase and the
Nbbased solid solutions. The carbide nanoparticles precipitating on grain boundaries increase the hardness
HV of the alloys by almost 30%: from 12.75 to 18.13 GPa for the samples corresponding to the intermetallic
phase and from 4.76 to 6.85 GPa for the samples corresponding to solid solutions.