Ductile-phase toughening and fatigue crack growth in Nb_3Al base alloys

摘要

Niobium aluminide (Nb_3Al) base intermetallic compounds exhibit good high-temperature strength and creep properties and potential for applications above 1200 ℃ provided their inadequately low room-temperature ductility, fracture toughness and fatigue crack growth behavior are improved. However. Nb,Al exists with a body centered cubic (bcc) Nb-rich solid solution (Nbss) over a wide composition range between ≈ 9 to ≈ 18 mol pet Al and offers the possibility of manufacturing in-situ composites with a ductile bcc Nbra [1]. In general, incorporation of ductile-phase improves the room-temperature ductility, fracture toughness, and fatigue crack growth behavior of composite materials. Ductile-phase toughening in binary Nbss/Nb3Al has been reported [2]. Nbss/Nb3Al composites prepared by vacuum hot pressing andreaction sintering elemental powders exhibited high fracture toughness (= 6.5 MPa√m) compared with the monolithic Nb3Al (≈1.1 MPaVm) [2]. Fatigue crack growth behavior of the two-phase alloys was superior compared with the Nb_3Al single phase alloys [2].