Formation of the (Ti, V)(C, N) Multicomponent Solid Solution by Mechanical Alloying of the TiPT-4–VN-CGr Powder Blend

Mechanically alloyed composite materials were obtained from the mixture of Titanium PT-4 grade (TiH2–Ti mixture), VN and graphite powders. A detailed X-ray diffraction (XRD) study of the phase composition was provided for the test samples at every 2 hours processing in a planetary ball mill. The refinement of crystal structures of VN and TiH2 phases present in the mixtures obtained has revealed that during the experiment (16 h of processing) the interaction between components of the charge occurs in two stages. Namely, the process of formation of vacancies in VN phase dominates at the first stage of synthesis (up to 5 h of treatment) with the subsequent penetration of released vanadium atoms into the tetrahedral voids of the TiH2 structure. At the same stage, the interaction of TiH2 titanium hydride with carbon atoms takes place, resulting in the formation of a  TiV0.33H0.66С0.22 compound, which is gradually decomposing at further processing. At the second stage of mechanochemical synthesis (5-16 h of processing), titanium atoms formed as a result of the destroying of the -Ti structure, are immersed in the VN crystal structure and the formation of a multicomponent (Ti, V)(C, N) solid solution takes place. XRD, SEM and EDS analysis have shown that the final product of mechanochemical synthesis contains the same amount of V0.67Ti0.33N solid solution based on VN nitride and equiatomic (Ti, V)(C, N) solid solution, the formation of which during mechanical alloying is detected for the first time. Analysing the kinetics of interaction of the components of TiPT-4-VN-CGr charge, it was shown that the extreme shock loads and deformations that occur during mechanical alloying (MA) cause a high degree of structural instability of the phases and lead to close contact between the grains, activating the flow of diffusion processes. All this stimulates the process of a cold sintering and creates the conditions for further formation of the multicomponent solid solutions. However, considering the participation of nitrogen atoms in the diffusion processes, the formation of (Ti, V)(C, N) solid solution and its full densification is possible only at sintering of the MA mixture at high temperatures.