The Fe-Al Intermetallic Compound High Temperature Alloy
Introduction
Intermetallic compounds are compounds, typically limited to binary systems or higher order compounds, composed of two or more metals. For centuries, alloys have been used for various applications due to their superior properties such as strength, wear resistance, and corrosion resistance. The Fe-Al intermetallic compound is one such system that is suitable for high temperature alloys.
Fe-Al intermetallic compounds are known for their superior mechanical properties such as high strength and excellent ductility, thus making them ideal candidates for use in high temperature alloys. Furthermore, Fe-Al alloys have low melting points and high thermal stability, giving them the advantage of maintaining mechanical properties over a wide range of temperatures. In addition, these alloys possess a great thermal shock resistance, making them suitable for the manufacturing of components and parts that will experience sudden temperature changes.
The Fe-Al system is composed of two classes of compounds: the ordered and disordered intermetallic compounds. The ordered compounds show higher strength and better ductility than the disordered compounds. The ordered compounds can be further divided into “ordered σ-type” and “ordered γ/γ*-type” compounds.
The ordered σ-type compounds are the most common of the ordered Fe-Al intermetallic compounds and are typically composed of Fe and Al atoms arranged in a face-centered cubic (fcc) lattice. The most common σ-phase in Fe-Al alloys is the Fe2Al5 variety. This variety has excellent mechanical property combinations such as high strength and good ductility.
The γ/γ*-type compounds are also known as “ordered ε-type” or “semi-ε-type”. Heavier elements like Cr, Co, and Ti may also be present in these compounds. These compounds are more thermally stable than the σ-type, allowing them to possess higher ductility and strength at elevated temperatures. Examples of γ/γ*-type compounds include FeAl3, FeAl6, and FeAl9.
Synthesis
The synthesis of the Fe-Al intermetallic compounds typically involves a combination of physical vapor deposition (PVD) or chemical vapor deposition (CVD), or spark plasma sintering (SPS). The deposition allows for the formation of the stable ordered/disordered compounds with very uniform properties; SPS is used for the rapid consolidation of the compounds into the desired shape.
Applications
Due to the superior properties of the Fe-Al intermetallic compounds, they have been used in various high temperature applications. Such applications include turbine blades and vanes of aircraft engines, turbine housings and other internal components of automotive exhaust systems, and other engine components. The combination of high strength and low weight makes the Fe-Al intermetallic compounds ideal for aerospace applications such as spacecraft and satellites.
In addition, these intermetallic compounds are used in advanced ceramics, as well as other components that require superior performance at elevated temperatures. Due to their superior thermal shock resistance, the compounds are also ideal for thermal spray coatings and other high-performance parts that will be exposed to thermal cycling and sudden temperature changes.
Conclusion
Fe-Al intermetallic compounds have been used in various high temperature applications due to their superior properties such as high strength and good ductility. The combination of PVD or CVD and SPS has allowed for the formation of stable compounds with uniform properties that can be used in high temperature applications such as turbine blades and vanes, aerospace components, and advanced ceramics. Furthermore, the high thermal shock resistance makes these compounds ideal for thermal spray coatings and other components that will be exposed to sudden temperature changes.
