Microstructure and elevated-temperature mechanical properties of in situ Ti2AlNb-reinforced TiAl-matrix composite prepared by powder metallurgy. (September 2020)

• Record Type: Journal Article
• Authors: Liang, Xiaopeng; Liu, Zhenqi; Li, Huizhong; Chen, Feihu; Yang, Wenfeng; Ouyang, Sihui; Liu, Yong; Wang, Li
• Is Part Of: Materials today communications. Volume 24(2020)
• Publication Date: 2020-09
• Subjects: TiAl intermetallic composite -- In situ formation -- Ti2AlNb phase -- Elevated-temperature mechanical properties -- Microstructure -- Strength–ductility product; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2020.101179
• Languages: English
• ISSNs: 2352-4928

Abstract

Highlights: An in-situ Ti2 AlNb reinforced TiAl matrix composite was successfully prepared. The composite exhibits excellent elevated temperature strength-ductility balance. The microstructure evolution was reasonable explained by establishing the models. The elevated temperature properties are related to the volume fraction of Ti2 AlNb. Abstract: An in situ Ti2 AlNb-reinforced Ti–45Al–5Nb–0.3 W-based intermetallic composite was prepared using 2 vol. % Nb powder and TiAl pre-alloy powder. The microstructure evolution and elevated-temperature mechanical properties of the Ti2 AlNb/TiAl composite were investigated. The results show that during the hot isostatic pressing (HIP) process, Nb diffused into the TiAl matrix, and formed Nb-rich particles in which an Nb-rich-region and the coarse rod-like Ti2 AlNb phase existed. After hot extrusion, the Nb-rich particles elongated along the direction of extrusion. Further, the mean diameter of the Ti2 AlNb phase regions decreased, and the Ti2 AlNb content increased. After heat treatment at 1280 °C for 1 h, the rod-like Ti2 AlNb phase regions in the extruded specimen transformed into needle-like and fine lath-like structures, and the proportion of Ti2 AlNb in the Nb-rich-regions increased. The extruded Ti2 AlNb/TiAl specimen shows a high tensile elongation (TE), and the heat-treated specimen shows a high yield strength (YS) and ultimate tensile strength (UTS) at the test temperatures of 750 °C–900 °C. In particular, the extruded specimen shows excellent strength–ductility product (UTS × TE) values of 38.8 GPa% and 46.9 GPa% at 800 °C and 850 °C, respectively. The high toughness of TiAl intermetallic composites was because of the fibrous tough Nb-rich-regions that contained the fine Ti2 AlNb phase.