A.V. Kartavykh

Application of Microstructured Intermetallides in Turbine Manufacture. Part 1: Present State and Prospects (A Review)

The objective of the present work is the analysis of the present state and prospects of the development of competitive technologies for creating microstructured materials of the class of intermetallides and their application in turbine and engine manufacture. The present review examines the general strategy of the development of the industry of heat-resistant materials of the class of intermetallides. A comparative analysis of the specific properties, advantages, and disadvantages of titanium, nickel, and iron aluminides and transition metals (Nb, Mo, and Ti) silicides in view of their application in construction of aircraft engines and gas-burning power-generating turbines is performed. The state and prospects of the development of competitive pilot technologies of manufacture and application of the above materials are analyzed.

Application of microstructured intermetallides in turbine manufacture. Part 2: Problems in development of heat-resistant alloys based on TiAl (a review)

The problems of formation of the necessary microstructure of intermetallic materials providing the required mechanical properties under extreme operating conditions are considered by the example of doped TiAl intermetallides. The problem of corrosion stability of intermetallides under extreme operating conditions is examined.

The Direct Observation of Grain Refinement Mechanism in Advanced Multicomponent γ-TiAl Based Structural Intermetallics Doped with Boron

The synthesis of Ti–44Al–5Nb–2Cr–1.5Zr–0.4B–0.07La and Ti–44Al–5Nb–1Cr–1.5Zr–1B–0.17La (at.%) intermetallic alloys was performed from pure metals by the electron beam semi-continuous casting technique. Alloys are characterized by convoluted microstructure whose refinement is progressive with the boron content increase. The specimens were analyzed using JEOL JSM6610 scanning electron microscope (SEM ) equipped with electron backscatter diffraction and energy dispersive X-ray spectroscopy (EDX ) systems. The boron alloying causes precipitation of micro-dimensional complex (Ti,Nb)B borides within solidifying melt. These particles-inoculants promote the formation of finer microstructure. Auger spectrometry was applied for quantitative elemental analysis of borides, using PHI-680 device. It was proven that the origin of structure refinement consists in solid-phase seeding and germination of α2-Ti3Al-phase on (Ti,Nb)B ribbon-like colonies with subsequent growth of α2-laths through the volumetrically prevailing γ-TiAl domains. We fixed several consecutive stages of microstructure refinement process. The description of these stages is supported with the dimensional, crystallographic and compositional characterization of microstructural constituents. The work provides a basis for new techniques of microstructure/mechanical properties engineering of studied materials.

Advanced Heat-Resistant TiAl (Nb,Cr,Zr)-Based Intermetallics with the Stabilized β(Ti)-Phase

The paper represents a brief review of authors’ research results and publications in the area of materials science and engineering of innovated lightweight heat-resistant TiAl-based intermetallic alloys. The system TiAl(Nb,Cr,Zr) under development is being considered as the advanced basis for the creation of TiAl-intermetallics of 3rd generation (TNM) TiAl(Nb,Mo)-like alloys, those being the most promising nowadays for an application in aviation jet engines design. This research is implemented within the frame of Federal Targeted Program for R&D in Priority Areas of Development of the Russian Scientific and Technological Complex for 2014–2020 (Russian FTP for R&D 2014–2020).

Microstructure/Properties Relationship of Advanced Heat-Resistant Intermetallics TiAl(Nb,Cr,Zr) After Casting and Float Zone Processing

New Ti-44Al-5Nb-3Cr-1.5Zr (at.%) β-stabilized intermetallic alloy was synthesized by the electron beam casting and afterwards re-solidified by the high-gradient (300 °C cm−1) induction float zone (FZ) technique. FZ-processing led to the ordered microstructure creation consisting of volumetrically prevailing (γ + α2) lamellar colonies separated by minor seam-like γ-granular interlayers, and the least intergranular quota of β(Ti)/B2 phase. The optimum phase balance, submicron interlamellar spacing and preferable alignment of lamellae along the thermal gradient were controlled by FZ-conditions. Unique microstructural adjustment enhances drastically the high-temperature yield strength, Young modulus and creep resistance. Thus the thermal limit of γ-TiAl(Nb,Cr,Zr) structural applicability could be extended from 750–800 °C towards 900–950 °C.