Failure of intermetallic TiAlCrNb alloys prepared by powder metallurgy

The results of fractographic investigations of intermetallic Ti-48Al-2Cr-2N b alloys prepared by powder metallurgy are presented in the paper. Elementa ry Ti, Al, Cr, and Nb powders were used as a starting material for the spec imen preparation. Powders were dry mixed in an attritor. The homogeneous mi xture was compacted by cold isostatic pressing. The material has undergone simple (S) and double (D) extrusion. After that hot isostatic pressing and heat treatment followed. Mechanical properties in relation to the microstru cture of intermetallic TiAlCrNb alloys were evaluated. At room temperatures the material D had a higher strength (511 MPa) than the material S (382 MP a). At higher temperatures the strength properties decreased to 430 MPa (D) and 370 MPa (S). The plastic properties were relatively low, less than 5 % , for all cases. The SEM investigation revealed that transcrystalline cleav age of gamma -phase and transcrystalline cleavage of lamellar colonies are the main fracture mechanisms at room temperatures. Transcrystalline cleavag e of lamellar colonies and intercrystalline separation are dominant at high er temperatures.