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a b s t r a c tIn a b-stabilized Ti-43Al-4Nb-1Mo-0.1B alloy (composition in atomic percent) the correlation between the occurrence of b-phase and temperature was analyzed experimentally and compared to thermodynamic calculations. Results from in situ high-energy X-ray diffraction, texture measurements, heat treatments, scanning electron microscopy, and temperature-dependent flow stress measurements were used to study the evolution of the b-phase with temperature. Thermodynamic calculations based on the CALPHAD method were applied to correlate the phases developed in the b-solidifying TiAl based alloy under investigation. This alloy is characterized by an adjustable b-phase volume fraction at temperatures where hot-work processes such as forging and rolling are conducted. Due to a high volume fraction of bphase at elevated temperatures the hot-extruded alloy can be forged under near conventional conditions.

Abstract. Development and processing of high-temperature materials is the key to technological progress in engineering areas where materials have to meet extreme requirements. Examples for such areas are the aerospace and automotive industries. New structural materials have to be stronger, stiffer and lighter to withstand the extremely demanding conditions in the next generation of aero-and automotive engines. Intermetallic γ-TiAl based alloys exhibit numerous attractive properties which meet these demands. These properties include high melting point, low density, high specific elastic modulus, good oxidation and burn resistance, and high specific strength up to application temperatures of 700 to 800°C. Thus, current γ-TiAl based alloys outperform advanced Ti-based alloys and have the potential to replace heavy Ni-based superalloys.

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An Proben aus dem Titanaluminidwerkstoff Ti48A12Cr mit unterschiedlichen Gefuge-und Oberflachenbearbeitungszustanden wurden rontgenografische Spannungsmessungen durchgefuhrt. Gemessen wurde an dem (224) X-Ray Stress Measurements on Ti48AlPCr Titanium Alurninide MaterialStresses in specimens of Ti48A12Cr material with various microstructures and surface conditions were measured by X-ray diffraction. The measurements were performed on the (224)/(422) twin peak of the y-phase with CuKcc-radiation by means of a position sensitive detector with metal wire. Depending on the m a s h i n g condition of the surface residual stresses between ca.-I300MPa (compression) and + 500MPa (tension) were found. The X-ray elastic constants -s, and 112 s2 were determined with flat specimens subjected to four point bending stresses. Results and measuring conditions are discussed with respect to problems with coarse grain, titanium fluorescence, peak selection and long measuring times.

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