Papers by Keyword: Titanium Aluminides

Abstract: The alloy design and efficient routes of TiAl processing are important technological challenges for the development of new aerospace systems. Gamma-TiAl alloys are potential replacements for nickel and conventional titanium alloys in hot sections of turbine engines, as well as in sub-structures of orbital platform vehicles. Powder metallurgy (P/M) of Ti-based alloys may lead to the obtainment of components having weak-to-absent textures, uniform grain structure and higher homogeneity compared with conventional wrought products. This paper aims to investigate the microstructural evolution and densification aspects involved in the obtainment of Ti-48Al-2Cr-2Nb (at.%) alloy by three P/M-processing routes. Samples were prepared from elemental and pre-alloyed powders mixed for 2 h, followed by cold uniaxial and isostatic pressing followed by sintering and hot pressing stages between 1100°C up to 1400°C, for 1 h. After metallographic preparation, sintered samples were characterized by means of scanning electron microscopy (SEM) in the backscattered mode (BSE), X-ray diffraction (XRD), and density measurements. The results showed the potential of TiAl pre-alloyed powders to prevent Kirkendall porosity. A full lamellar microstructure was obtained by the pressureless route while a duplex microstructure was observed in samples produced by the hot pressing route.

Abstract: The influence of basic high-temperature synthesis parameters on the process of structure formation in the mechanically activated powder mixture 3Ti+Al was investigated in the study. The synthesis was realized by the method of induction heating in the thermal explosion mode. The heating temperature of the mixture reached 1500°C during the solid state reaction. This temperature exceeded the adiabatic combustion temperature. The investigations of the phase structure formation processes were conducted by XRD methods. In order to obtain a Ti₃Al single-phase compound, the optimal time-temperature parameters of the synthesis were determined.

Abstract: In this paper growingtheintermetalliclayers at the interfaces of explosively welded titanium and aluminum plates have been investigated. It was shown that explosion welding was the efficient technology for forming multilayered stacks consisted of dissimilar materials. This method provided the firm joint formation between metallic plates. Heat treatment of explosively welded workpieces allowed obtaining the Al₃Ti intermetallic phase at titanium-aluminum interfaces. Formation of intermetallic layer proceeded inhomogeneously in cross-section of the composite due to the structural particularities of interfaces and adjacent arias formed during the explosion welding process. The titanium aluminide growth ratedecreased corresponding to increaseof the intermetallic layer thickness. Intermetallic phase is notable for its high hardness and elasticity. Microhardness and Young’s module in the composite explosively welded and annealed at 640 ^оС reached 7.5 GPaand 280GPa respectively.

Abstract: Particularities of the multilayered “Ti – Al₃Ti” composites structure formation were investigated. Spark plasma sintering of Ti and Al plates in cylindrical molds at the temperature of 830 ^оС and pressure of 3 kN during 5 minutes was found to be the most efficient technology of formation of materials with intermetallic layers. The regime described above allows fabricating material with high-quality intermetallic layers and with microhardness level up to 3800 MPa.