Institute of Materials Science, Khabarovsk Research Center, Far Eastern Branch of RAS, Khabarovsk, Russia:

I. A. Astapov, Senior Researcher, e-mail: immaterial_khv@mail.ru
N. M. Vlasova, Researcher
T. B. Ershova, Head of Laboratory of Composite Materials
E. A. Kirichenko, Researcher

Currently, the development of new composite materials is an urgent task. The combination of properties in multiphase material provides advantages that can be used in aircraft and machine building, including the development of functional coatings and powders. Of these materials it is possible to distinguish composites based on MAX-phases, which are characterized by increased characteristics of heat resistance, elasticity, ease of machining, etc. Materials of composition (3Ti:Al) + 15% SiC were obtained by cold pressing and subsequent hightemperature sintering in vacuum. As initial components, chemically pure titanium, aluminum and silicon carbide were used. Thermal analysis was carried out, and phase composition and microstructure were studied. It is shown that the formation of the target phases — Ti₂AlC and titanium carbosilicide — occurs in several stages and proceeds relatively slowly. On the DTA curve, only one characteristic exothermic peak corresponding to the synthesis of titanium aluminide can be observed. Phase analysis showed that at low temperatures (up to 1000 ^оС), an intermetallic compound of titanium with aluminum is formed. At the same time, the silicon carbide lattice is restructured with the concomitant formation of TiC and at a temperature above 1100 ^оС — by the formation of Ti₅Si₃C_x. The MAX phase of Ti₂AlC is the result of the interaction of Ti₃Al with the carbon atoms released during the reaction of silicon carbide with titanium. The microstructure investigation indicates the final stage of sintering at temperatures above 1300 ^oC. At lower values in the structure, individual grains of TiC, SiC, and Ti₃Al intermetallide regions are noticeable. The sample, sintered at T = 1400 ^оС, is a two-phase composite material, in each grain of which Ti₂AlC and Ti₅Si₃C_x are evenly distributed. There were no other phases in these samples. The microhardness of two-phase grains is HV50 = 7.2 GPa, while the hardness numbers are in the range 3.0–9.0 GPa, which is explained by the influence of the ratio of the two phases at the place of indentation.

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