Microstructure stability of Ti2AlN/Ti-48Al-2Cr-2Nb composite at 900 °C
(State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: Microstructure stability of in situ synthesized Ti2AlN/Ti-48Al-2Cr-2Nb composite during aging at 900 °C was investigated by XRD, OM and TEM, and the unreinforced Ti-48Al-2Cr-2Nb alloy was also examined for comparison. The result showed that in the TiAl alloy, α2 lamellae thinned and were broken down, and became discontinuous with increasing aging time. The decomposition of α2 lamella to g which was characterized by parallel decomposition and breakdown of α2 lamellae led to the degradation of the lamellar structure. While in the composite, lamellar structure remained relatively stable even after aging at 900 °C for 100 h. No breakdown of α2 lamellae except parallel decomposition and precipitation of fine nitride particles was observed. The better microstructural stability of the composite was mainly attributed to the precipitation of Ti2AlN particles at the α2/g interface which played an important role in retarding the coarsening of lamellar microstructure in the matrix of composite.
Key words: TiAl composite; Ti2AlN; microstructure stability; lamellar structure; precipitation