TiAl based Metallic Intermetallic Composites for High Temperature Alloys
Recent studies have been focusing on the use of TiAl based metallic intermetallic composites (MICs) as high temperature alloys. The ability of MIC strengthen and reinforce materials has already been recognized when TiAl base materials were first developed by industrial companies in the early 1980s. Since then, multiple research works have been conducted to identify and improve their ductility and oxidation resistance, especially under high stress conditions.
The advantages of TiAl base metallic intermetallic composites (MICs) are numerous. Not only are they more thermally stable than other materials, they also possess better creep, fracture toughness and wear properties. Additionally, they have the potential to operate in temperatures up to 1000o C and higher, making them applicable to a variety of high temperature applications. Compared to conventional high temperature superalloys, MICs provide improved corrosion resistance and fatigue properties as well.
The formation of TiAl base MICs occurs through the atomic diffusion of aluminum into titanium matrix during heat treatment. Various elements (such as carbon, cobalt, chromium, manganese, and nickel) are added to TiAl base materials to modify the mechanical properties. The microstructure of the resulting matrix consists of lamellar or globular TiAl particles, dispersed with an ordered distribution along with their chemically consistent alloys (TiAl4C4, Ni3Al3Ti3, Ni3Al3 Ti3 (Co, Mn), and Ti3Al-Cr etc.).
The microstructure of a TiAl -based composite greatly affects its mechanical behavior. To create specific microstructural features, different variants of heat treatment such as aging, solutionizing and homogenization are used. Furthermore, advanced heat treatments such as pulsed current treatments and cryogenic treatments can be used to tailor the microstructural characteristics of TiAl-based MICs. The MIC materials exhibit low grain boundary densities combined with a high fraction of finely dispersed oxide inclusions, which results in excellent strength-ductility combinations.
Current research efforts are directed towards improving the corrosion resistance of TiAl base MICs and reducing their cost.To this end, various strategies are being developed such as surface treatments, increased grain boundary phases, and the addition of corrosion-resistant elements.
In conclusion, TiAl base metallic intermetallic composites have a wide range of capabilities and a potential to perform better than traditional high temperature alloys, making them an attractive option for a variety of high temperature applications. As research efforts continue to evolve, the potential of this versatile material looks promising.
