Microstructure and fracture toughness of a TiAl-Nb composite consolidated by spark plasma sintering
(1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. State Key Laboratory of Porous Metal Materials, Northwest Institute for Nonferrous Metal
Research,
Xi’an 710016, China;
3. National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials,
South China University of Technology, Guangzhou 510641, China)
2. State Key Laboratory of Porous Metal Materials, Northwest Institute for Nonferrous Metal
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*Corresponding author. Tel: +86 29 86231095. Fax: +86 29 86231103 E-mail address: xizp_nin@163.com (Zhengping Xi) |
Xi’an 710016, China;
3. National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials,
South China University of Technology, Guangzhou 510641, China)
Abstract: A TiAl-Nb composite was prepared by spark plasma sintering (SPS) at 1250 °C and 50 MPa for 5 min from prealloyed TiAl powder and elemental Nb powder in a molar ratio of 9:1 for improving the fracture toughness of TiAl alloy at room temperature. The microstructure, phase constitute, fracture surface and fracture toughness were determined by X-ray diffractometry, electron probe micro-analysis, scanning and transmission electron microscopy and mechanical testing. The results show that the sintered samples mainly consist of γ phase, O phase, niobium solid solution (Nbss) phase and B2 phase. The fracture toughness is as high as 28.7 MPa∙m1/2 at room temperature. The ductile Nbss phase plays an important role in absorbing the fracture energy in front of the cracks. Moreover, B2 phase can branch the propagation of the cracks. The microhardness of each phase of the composite was also tested.
Key words: TiAl-Nb composite; fracture; spark plasma sintering (SPS); powder metallurgy; fracture toughness; fracture energy; crack propagation