Effect of nitrogen addition and aging treatment on microstructure and high temperature mechanical properties of Ti-48Al-2Cr-2Nb (at%) intermetallic alloy

Effects of nitrogen (N) addition (0.5, 1, and 2 at%) on microstructure formation and high temperature mechanical properties of the age-hardened Ti-48Al-2Cr-2Nb (4822, at%) intermetallic alloy were in-vestigated. Alloys were fabricated by vacuum arc re-melting followed by hot isostatic pressing, solution annealing, and finally aging at two different conditions of 700 degrees C/10 h or 900 degrees C/1 h. Mechanical properties of the age-hardened samples were investigated via small punch testing at 800 degrees C. Results showed that N addition resulted in microstructure refinement and increased uniformity of microstructures and mechanical properties. Lamella coarsening and fragmentation was occurred during both aging conditions; however, a more stable lamellar microstructure was achieved by N addition. Colonies with various lamellar orientation showed different fragmentation behavior. Better mechanical properties was achieved in the alloy containing 1 at%N after aging at 900 degrees C/1 h. Inter-lamellar fracture was the predominant fracture mechanism in all intermetallic alloys.(c) 2022 Elsevier B.V. All rights reserved.