OPTIMIZING THE PROPERTIES OF TIAL SHEET MATERIAL FOR APPLICATION IN HEAT PROTECTION SHIELDS OR PROPULSION SYSTEMS

The present work represents a survey on the production of TiAl sheet m aterial on an industrial scale and on the properties of these sheets. Using different final heat treatments, near-gamma and duplex microstru ctures have been produced. The mechanical properties as a function of the microstructure have been examined at room temperature (RT) and 700 degrees C. Additionally, the parameter field of temperature and strai n rate for which superplastic forming of the sheet material is possibl e has been established. Mechanical testing at RT revealed that the str ength of Ti-48Al-2Cr sheet material is mainly governed by grain size i f the microstructure is homogeneous. The volume fraction and distribut ion of the second phase (alpha(2)-Ti3Al) appears to be of minor influe nce. Room temperature ductilities between 0.25 and 0.051 have been mea sured. At 700 degrees C the duplex microstructures show slightly impro ved strength compared to near-gamma microstructures. Depending on the deformation rate, fracture strains between O.11 and 0.80 have been det ected. Superplastic behaviour of Ti-48Al-2Cr (at.%) is governed by dyn amic recrystallization or dynamic grain growth, depending on the initi al grain size and the deformation parameters temperature and strain ra te.