摘要
In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in constructing the TiAl-based laminated composites.In this work,TiAl/Ti_(2)AlNb laminated composites are successfully synthesized by vacuum hot pressing combined with the foil-foil(sheet)metallurgy.Under the pressure of 65 MPa,different holding time and temperature of hot pressing are tried and the optimized fabrication parameter is acquired as 1050℃/120 min/65 MPa.Along with the changes of processing parameters,the defect,microstructure,interface,phase transformation and the corresponding mechanical properties are detailly discussed.The results show that the TiAl/Ti_(2)AlNb laminated composite fabricated at 1050℃ for 2 h achieves a good metallurgical interface bonding.The corresponding interface microstructure is composed of region I and region II.The region I consists of O,α_(2)and B2/βphase,and region II is made up ofα2.Subsequently,the tensile tests indicate that the composite synthesized at 1050℃ for 2 h possesses a maximum strength of 812 MPa and a total elongation of 1.31%at room temperature,and a strength of 539.71 MPa and the highest total elongation of 10.34%at 750℃.The well synergistic deformation ability between the interface and the two base alloys endows the composite an excellent tensile performance.Moreover,the composite processed at 1050℃ for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m^(1/2)and 30.1 MPa.m^(1/2),respectively.The Ti_(2)AlNb alloy in the laminated structure effectively release the stress around the crack tip and plays a role in toughening.Further,crack deflection,crack bridging,crack blunting and fragmentation also make contributions to enhance the fracture toughness of the laminated composites.
基金
supported by Major Special Science and Technology Project of Yunnan Province 202002AB080001-3
the National Natural Science Foundation of China(no.51704088)
Fundamental Research and Development Program of China(Grant no.JCKY2017205B032)。
