Progress in superplasticity of intermetallics - review

The intermetallic phases possess a combination of outstanding properties, such as high strength and corrosion resistance at high temperatures and low density, which make them particularly attractive for high temperature applications. However, their inherent room temperature brittleness impeded their applications in high temperature structural applications up to date. Recent developments in improving their room temperature ductility by alloying and thermomechanical processing have stimulated an extensive research activities to modify their properties and to produce near-net shape parts by various methods for automotive and aerospace applications. Recently, superplastic behaviour (up to 1000% elongation) in various intermetallics were reported. This is striking since these materials are quite brittle at room temperature. However, they can be superplastically formed at elevated temperatures provided that the initial grain size is sufficiently fine and the grain growth can be suppressed during deformation. These advancements make intermetallics excellent candidates for high temperature applications. When convenient superplastic forming processes are established and incorporated with diffusion bonding (SPF/DB) as in Ti-alloys the production of intermetallic light-weight complicated structural components for high temperature applications can be realized in one step, which has well known economic advantages over other manufacturing techniques. The aim of this review is to outline the state-of-art developments in superplastic forming and diffusion bonding of intermetallics, especially Ti-Al intermetallics including #gamma#-TiAl developed at GKSS, and to discuss its future prospects to manufacture structural components for elevated temperature applications. (orig.)98 refs.Available from TIB Hannover: RA 3251(96/E/3) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman