We determined the compactability regularities observed during the cold uniaxial pressing of layered powder green samples, taking into account factors such as composition, height, and number of Ti–B (TiB) and Ti–Al–Nb–Mo–B (TNM) layers. The following composition was chosen for the TNM layer at %: 51.85Ti–43Al–4Nb–1Mo–0.15B, while for the Ti-B layer we selected the composition wt %: Ti-B-(20, 30, 40) Ti. Green samples were made containing both 100 vol % TiB and TNM, and those taken in the following proportions, vol %: 70TiB/30TNM, 50TiB/50TNM, 30TiB/70TNM; multilayer green samples were studied in the following proportions, vol %: 35TiB/30TNM/35TiB, 25TiB/25TNM/25TiB/25TNM, 35TNM/30TiB/35TNM. Based on the obtained rheological data, we determined the rheological characteristics of the layered green samples, including compressibility modulus, compressibility coefficient, relaxation time, and limiting value of linear section deformation. These characteristics were found to vary depending on the composition, height, and number of layers. Our findings revealed that reducing the TNM content in the charge billet composition improves the compaction of powder materials under the given technological parameters of uniaxial cold pressing. Moreover, we observed that increasing the boron content and decreasing the amount of titanium in the Ti–B composition enhances the compactability of powder materials. We also established a relationship between the compaction pressure interval and the density of the layered powder green sample.
This study investigates TNM-type titanium aluminide alloys, representing the third generation of β-stabilized γ-TiAl heat-resistant materials. The aim of this work is to study the combustion characteristics and to produce compact materials via the free SHS compaction method from initial powder reagents taken in the following ratio (wt%): 51.85Ti–43Al–4Nb–1Mo–0.15B, as well as to determine the effect of high-temperature isothermal annealing at 1000 °C on the structure and properties of the obtained materials. Using free SHS compression (self-propagating high-temperature synthesis), we synthesized compact materials from a 51.85Ti–43Al–4Nb–1Mo–0.15B (wt%) powder blend. Key combustion parameters were optimized to maximize the synthesis temperature, employing a chemical ignition system. The as-fabricated materials exhibit a layered macrostructure with wavy interfaces, aligned parallel to material flow during compression. Post-synthesis isothermal annealing at 1000 °C for 3 h promoted further phase transformations, enhancing mechanical properties including microhardness (up to 7.4 GPa), Young’s modulus (up to 200 GPa) and elastic recovery (up to 31.8%). X-ray powder diffraction, SEM, and EDS analyses confirmed solid-state diffusion as the primary mechanism for element interaction during synthesis and annealing. The developed materials show promise as PVD targets for depositing heat-resistant coatings.
A mathematical model was developed to determine the order of failure of layers in a two-layer ceramics composite and to determine the conditions for achieving the maximum limit load under three-point loading. The model was set in the space of three “bilayer parameters”: the ratio of the thickness of the lower layer to the whole thickness of the beam, the ratio of Young’s moduli of the lower layer to the upper layer, and the ratio of flexural strengths of the materials of the lower layer to the upper layer. The adequacy of the model obtained was confirmed by experimental results on the three-point bending of the experimental specimens. The experimental samples were two-layer composites consisting of a cermet layer TiB/Ti and a layer of α-Ti. The samples were obtained by free self-propagating high-temperature synthesis (SHS) compression and with varying their thickness. The results obtained make it possible to predict in advance which layer, based on the specific bilayer parameters, will trigger the brittle fracture mechanism as well as to set the maximum destructive load of bilayer composites.
24 September 2025 in Inorganic Materials: Applied Research
Experimental studies were conducted on the high-temperature forming of materials based on TiB/TiAl(Nb, Mo)B under process conditions that combine combustion in the mode of self-propagating high-temperature synthesis (SHS) of the initial powder components and their shear deformation following the passage of the combustion wave—free SHS compression. The objects of study were composites consisting of 100% TiB–(20–40) wt % Ti (TiB layer) and TiAl(Nb, Mo)B alloy (at %: 51.85 Ti–43 Al–4 Nb–1 Mo–0.15 B), as well as two-layer composite materials with the following layer proportions, vol %: 70TiB/30TiAl(Nb, Mo)B, 50TiB/50TiAl(Nb, Mo)B, 30TiB/70TiAl(Nb, Mo)B. The degree of deformation was chosen as the criterion for formability of the composites during shear deformation. It was established that, by varying the composition of each layer in the composite and the technological parameters of free SHS compression, it is possible to regulate the degree of deformation from 0.2 to 0.55. It was shown that the technological parameters of free SHS compression (holding time, pressing pressure, deformation rate) and the initial composition affect the formability and structure of the composites. The structural features and phase composition of the composites obtained were studied. It was demonstrated that a diffusion zone forms between the ceramic and intermetallic layers as a result of chemical interaction, the size of which can be regulated within the range of 30–150 μm.