Design, Processing, Microstructure, Properties, and Applications of Advanced Intermetallic TiAl Alloys

• Published in: Advanced engineering materials Vol. 15; no. 4; pp. 191 - 215
• Main Authors: Clemens, Helmut, Mayer, Svea
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.04.2013; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Alloys; Aluminides; Applied sciences; Automotive engineering; Condensed matter: structure, mechanical and thermal properties; Creep; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Heat treatment; Hot working; Intermetallic compounds; Intermetallics; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Solidification; Titanium base alloys; Titanium compounds; Phase diagrams; Intermetallic compounds; Creep; Ductility; Nanostructures; Aeronautic industry; Fabrication property relation; Solidification; Design; Titanium alloys; Aluminium alloys; Automotive industry; Thermomechanical treatments; Peritectic reactions; Microstructure
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.201200231

After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ‐TiAl phase have found applications in automotive and aircraft engine industry. The advantages of this class of innovative high‐temperature materials are their low density and their good strength and creep properties up to 750 °C as well as their good oxidation and burn resistance. Advanced TiAl alloys are complex multi‐phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo‐mechanical processing and/or subsequent heat treatments. The background of these heat treatments is at least twofold, i.e., concurrent increase of ductility at room temperature and creep strength at elevated temperature. This review gives a general survey of engineering γ‐TiAl based alloys, but concentrates on β‐solidifying γ‐TiAl based alloys which show excellent hot‐workability and balanced mechanical properties when subjected to adapted heat treatments. The content of this paper comprises alloy design strategies, progress in processing, evolution of microstructure, mechanical properties as well as application‐oriented aspects, but also shows how sophisticated ex situ and in situ methods can be employed to establish phase diagrams and to investigate the evolution of the micro‐ and nanostructure during hot‐working and subsequent heat treatments. Development and processing of high‐temperature materials is the key to technological progress in engineering areas where materials have to meet extreme requirements. After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ‐TiAl phase have found applications in automotive and aircraft engine industry. This review gives a general survey of engineering γ‐TiAl based alloys, but concentrates on β‐solidifying γ‐TiAl based alloys, e.g., TNM™ alloys, which show excellent hot‐workability and balanced mechanical properties when subjected to adapted heat treatments.