In this paper, the structural characteristics of a W-Ta-Mo-Nb-V-Cr-Zr-Ti non-equiatomic refractory metal alloy obtained by spark plasma sintering (SPS) of a high-energy ball-milled powder mixture are reported. High-energy ball milling resulted in the formation of particle agglomerates ranging from several tens to several hundreds of micrometers. These agglomerates were composed of micrometer and submicrometer particles. It was found that, during ball milling, a solid solution of A2 structure formed. The grains of the sintered material ranged from fractions of a micrometer to several micrometers. During SPS, the phase transformations in the alloy led to the formation of a Laves phase of C15 structure and ZrO and ZrO₂ nanoparticles. The microhardness of the ball-milled alloy and sintered material was found to be 9.28 GPa ± 1.31 GPa and 8.95 GPa ± 0.42 GPa, respectively. The influence of the processing conditions on the structure, phase composition, and microhardness of the alloy is discussed.

Titanium carbide (TiC), is the most thermodynamically stable compound in the Ti–C–Cu system, which makes it a suitable reinforcement phase for copper matrix composites. In this work, the interaction of a Ti–Cu alloy with different forms of carbon was investigated to trace the structural evolution leading to the formation of in-situ TiC–Cu composite structures. The reaction mixtures were prepared from Ti₂₅Cu₇₅ alloy ribbons and carbon black or nanodiamonds to test the possibilities of obtaining fine particles of TiC using ball milling and Spark Plasma Sintering (SPS). It was found that the behavior of the reaction mixtures during ball milling depends on the nature of the carbon source. Model experiments were conducted to observe the outcomes of the diffusion processes at the alloy/carbon interface. It was found that titanium atoms diffuse to the alloy/graphite interface and react with carbon forming a titanium carbide layer, but carbon does not diffuse into the alloy. The diffusion experiments as well as the synthesis by ball milling and SPS indicated that the distribution of TiC particles in the composite structures obtained via reactive solid-state processing of Ti₂₅Cu₇₅+C follows the distribution of carbon particles in the reaction mixtures. This justifies the use of carbon sources that have fine particles to prepare the reaction mixtures as well as efficient dispersion of the carbon component in the alloy–carbon mixture when the goal is to synthesize fine particles of TiC in the copper matrix.

In this study, the synthesis of tungsten carbides in a copper matrix by spark plasma sintering (SPS) is conducted and the microstructure formation mechanisms of the composite materials are investigated. The reaction mixtures were prepared by the high-energy mechanical milling (MM) of W, C and Cu powders. The influence of the MM time and SPS temperature on the tungsten carbide synthesis in an inert copper matrix was analyzed. It was demonstrated that the milling duration is a critical factor for creating the direct contacts between the W and C reactants and increasing the reactive transformation degree. A WC–W₂C–Cu composite was fabricated from the W–C–3Cu powder mixture milled for 10 min and subjected to SPS at a temperature of 980 °C for 5 min. The formation of unconventional microstructures with Cu-rich regions is related to inter-particle melting during SPS. The WC–W₂C–Cu composite showed a promising combination of mechanical and functional properties: a hardness of 300 HV, an electrical conductivity of 24% of the International Annealed Copper Standard, a residual porosity of less than 5%, a coefficient of friction in pair with a WC-6Co counterpart of 0.46, and a specific wear rate of the material of 0.52 × 10⁻⁵ mm³ N⁻¹ m⁻¹.

Metallic-glass-reinforced metal matrix composites are a novel class of composite materials, in which particles of alloys with an amorphous structure play the role of reinforcement. During the fabrication of these composites, a crystalline metal is in contact with a multicomponent alloy of an amorphous structure. In the present work, the morphological features of the reaction products formed upon the interaction of Fe₆₆Cr₁₀Nb₅B₁₉ metallic glass particles with aluminum were studied. The composites were processed via spark plasma sintering (SPS), hot pressing or a combination of SPS and furnace annealing. The reaction products in composites with different concentrations of the metallic glass and different transformation degrees were examined. The products of the interaction of the Fe₆₆Cr₁₀Nb₅B₁₉ metallic glass with Al were observed as dense layers covering the residual alloy cores, needles of FeAl₃ protruding from the dense shells as well as needles and platelets of FeAl₃ distributed in the residual Al matrix. The possible role of the liquid phase in the structure formation of the reaction products is discussed. The formation of needle- and platelet-shaped particles presumably occurred via crystallization from the Al-Fe-based melt, which formed locally due to the occurrence of the exothermic reactions between aluminum and iron. At the same time, aluminum atoms diffused into the solid Fe-based alloy particles, forming an intermetallic layer, which could grow until the alloy was fully transformed. When aluminum melted throughout the volume of the composite during heating of the sample above 660 °C, a similar microstructure developed. In both Al–Fe₆₆Cr₁₀Nb₅B₁₉ and Al–Fe systems, upon the reactive transformation, pores persistently formed in locations occupied by aluminum owing to the occurrence of the Kirkendall effect.

Reactive processing of metals is interesting for materials design and achieving new sets of properties. The transformation degree of the metals, the factor governing the properties of the material as a whole, depends on the sintering/heat treatment conditions. In the present investigation, the phase and microstructure formation of materials obtained by sintering of Cu-10 wt.% Al mixtures and layered Cu/Al structures under different modes of pressing/heating is presented. The samples were obtained via spark plasma sintering (SPS), hot pressing (HP) and pressureless sintering. The products of the interaction between the metals were Al₂Cu and Cu₉Al₄ intermetallics and Cu(Al) solid solutions. The influence of the consolidation method on the phase composition of the sintered materials was studied. The hardness of the composites was analyzed in relation to their structural features. A model experiment has been conducted to trace the structural evolution at the Cu/Al interface caused by interdiffusion. The Cu/Al layered structures obtained by detonation spraying of the powders on a steel substrate were treated by SPS or HP. The effect of electric current, which is a feature of SPS processing, was in accelerating the reaction product formation in the layered structures still containing the starting metallic reactants.

In this work, titanium carbonitrides were synthesized by self-propagating high-temperature synthesis (SHS) in nitrogen. For the first time, the synthesis of titanium carbonitrides by combustion was realized in nitrogen at atmospheric pressure. The synthesis was carried out by subjecting high-energy ball-milled titanium–carbon black powder mixtures to combustion in a nitrogen atmosphere. The influence of the ball milling time on the phase composition of the products of SHS conducted in the Ti+0.3C reaction mixture was studied. It was found that the titanium–carbon black mixtures need to be milled for a certain period of time for the combustion synthesis to yield a single-phase carbonitride product.