R. A. Gaisin

Microstructure and hot deformation behavior of two-phase boron-modified titanium alloy VT8

The results of studying the microstructure, compressive mechanical characteristics, and evolution of the microstructure of the cast two-phase titanium alloys VT8-xB (with x = 0, 0.2, and 0.4 wt %) during hot deformation are presented. Alloying with boron leads to the formation of borides, which are predominantly located at the boundaries of β grains and give rise to a considerable refinement of the original cast structure. The results of high-temperature compressive tests have shown that the strength characteristics of the boron-modified alloys noticeably exceed those of the base VT8 alloy. The experiments on the multiple isothermal forging of VT8 and VT8-0.4B alloys carried out at temperatures of 700–650°C have revealed the acceleration of the kinetics of dynamic recrystallization due to the presence of borides, which were efficiently refined during deformation. The alloying of the VT8 alloy with boron has been discussed from the viewpoint of improving the efficiency of the deformation treatment and final service properties of two-phase titanium alloys.

Microstructure and mechanical characteristics of VT1-0-Based composite material reinforced by titanium monoboride

The microstructure and mechanical characteristics of commercially pure titanium, i.e., the VT1-0 alloy, modified by 1.5 wt % B have been studied. It has been found that, during the melting of an ingot, uniformly distributed titanium monoboride (TiB) fibers up to Ø5 × 150 μm in size appear in the material in a volume fraction of about 8%. The results of compressive and tensile tests show that this composite material substantially surpasses pure titanium in the strength characteristics, with retaining satisfactory plasticity.

Structure and properties of Mo–9Si–8B alloy fabricated by casting

This article discusses the microstructure and mechanical properties under compression and resistance against oxidation of Mo–9Si–8B (at %) alloy fabricated by casting. Despite generation of coarse dendritic structure, the as-cast alloy demonstrates excellent high-temperature strength: the alloy yield strength at 1200°C is 700 MPa, and the maximum compression strength is 750 MPa, which is significantly higher than the strength properties at this temperature of the top quality heat-resistant alloys on the basis of nickel. The article considers possible improvements of the alloy resistance against oxidation by disintegrating the dendritic structure and obtaining a fine-grained structure, which promotes a more uniform distribution in the bulk of the matrix phase and disperse intermetallic phases.

Recrystallization behavior of boron-modified commercial-purity titanium during hot deformation

A comparative investigation of the recrystallization behavior of as-cast commercial-purity (CP) titanium VT1-0 with addition of 0.2 wt % boron and of unalloyed CP titanium in the hot-rolled and as-cast states has been performed. The introduction of boron leads to the formation of uniformly distributed short filaments and particles of titanium monoboride (TiB), which stimulates a substantial refinement of the cast structure. The recrystallization behavior of the alloys was studied after deformation by compression at T = 900-600°C using the EBSD analysis. It has been established that the kinetics of the recrystallization of the as-cast VT1-0-0.2B alloy is substantially accelerated compared with that of the unalloyed VT1-0 alloy due to the presence of borides. The recrystallization behavior of the VT1-0 alloy with the initial hot-rolled structure and of the VT1-0-0.2B alloy with the as-cast structure proved to be approximately similar. Based on the investigations performed, recommendations have been made that should facilitate (and reduce the cost of) the production of fine-grained and ultrafine-grained semi-finished items of CP titanium.