Abstract
Intermetallic compounds based on Ti-Al- (Si) are attractive materials with good thermal stability and low density. However, the production of these materials is quite complicated. Partially modified conventional methods of melting metallurgy are most often used due to availability, possible high productivity, and relatively low production costs. Therefore, some technologies for the production of intermetallics based on Ti-Al are currently available, but with certain disadvantages, which are caused by poor casting properties or extreme reactivity of the melt with crucibles. Some shortcomings can be eliminated by modifying the melting technology, which contributes to increasing the cost of the process. The work deals with the preparation of Ti-Al-Si intermetallic compounds with different contents of aluminum and silicon, which were produced by centrifugal casting in an induction vacuum furnace Linn Supercast-Titan. This process could contribute to the commercial use of these alloys in the future. For this research, the TiAl15Si15(in wt.%) alloy was selected, which represents a balanced ratio of aluminides and silicides in its structure, and the TiAl35Si5 alloy, which due to the lower silicon content allows better melting conditions, especially with regard to the melting temperature. This alloy was also investigated after HIP (“Hot Isostatic Pressing”) treatment.
Highlights
Extensive testing of alloys based on intermetallic compounds of the Ti-Al system, which has been carried out since the 1980s, has enabled their commercial application in the aerospace and automotive industries
Microstructure of both tested alloys consists of titanium silicide (Ti5Si3) particles in titanium aluminide (TiAl) matrix, see Figures 1 and 2
Hot isostatic pressing of the TiAl35Si5 casting led to partial spheroidization of the Ti5Si3 particles, leading to round shape of the silicide
Summary
Extensive testing of alloys based on intermetallic compounds of the Ti-Al system, which has been carried out since the 1980s, has enabled their commercial application in the aerospace and automotive industries. These TiAl-based alloys are highly alloyed mainly with niobium and small amounts of carbon and boron Due to their excellent mechanical properties and resistance to high temperature oxidation and creep up to 800 ◦C, they become suitable materials for various components in gas turbines, jet and automobile engines [3,4]. Due to the growing demands on these alloys with regard to aerospace components, which should be able to withstand ever-increasing temperatures, the latest fourth generation of TiAl-based alloys is being developed, represented by Ti46Al8Ta (at.%) alloy This compound is alloyed with tantalum, which significantly reduces the diffusion in the material for its strengthening, even at low cooling rates [4]
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