Effect of processing parameters on the microstructure and mechanical properties of TiAl/Ti2AlNb laminated composites

In order to improve the intrinsic brittleness of TiAl alloys, Ti2AlNb 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/Ti2AlNb 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 degrees C/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/Ti2AlNb laminated composite fabricated at 1050 degrees C 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, alpha(2) and B2/beta phase, and region II is made up of oz 2 . Subsequently, the tensile tests indicate that the composite synthesized at 1050 degrees C 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 degrees C. 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 degrees C for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m 112 and 30.1 MPa.m(1/2), respectively. The Ti2AlNb 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. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.

Automated summary

TiAl/Ti2AlNb laminated composites with excellent mechanical properties and metallurgical interface bonding have been successfully synthesized. The composite fabricated at 1050 degrees C for 2 h shows good tensile performance at both room temperature and high temperature.