INFLUENCE OF TEST TEMPERATURE ON FRACTURE OF TIALCRNB ALLOY
Abstract
Intermetallic Ti-48Al-2Cr-2Nb alloys manufactured from the elementary powders by two PM technologies were studied. The homogenized mixture was compacted by cold isostatic pressing (CIP), then deformed by hot single, or double extrusion, and finally compacted by hot isostatic pressing (HIP). The prepared materials were tensile tested at room temperature and 700°C. Mechanical properties were related to the production technology, test temperature, microstructure, fracture surfaces were analyzed, and fracture mechanisms were studied. The dominant fracture mechanisms were at room temperature transcrystalline cleavage of gamma phase and transcrystalline cleavage of lamellar colonies. On the other side, at 700°C for both tested materials transcrystalline cleavage of gamma phase decreased to less than 8%. Main mechanisms of fracture were transcrystalline cleavage of lamellar colonies and intercrystalline fracture of gamma grains. A fracture model of the very fine lamellar structure was proposed, and fracture mechanism was described for the obtained microstructure.
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