Superior tensile strength and microstructure evolution of TiB whisker reinforced Ti60 composites with network architecture after β extrusion

Abstract

The tensile properties (at room and high temperatures) and microstructure evolution after extrusion (1200°C) have been systematically investigated in TiBw/Ti60 composites with network architecture. The microstructure of matrix of composites shows that grain size was significantly refined and sufficient substructure was introduced after β extrusion. DRX occurred prior near TiBw region due to providing the nucleation site and having high driving force. Moreover, ordered α2 phase which is formed in sintering process was re-dissolved after extrusion. The as-extruded composite exhibits strong <0001>α//ED fiber texture which is transformed from <110>β//ED fiber texture based on Burgers' relationship, which are beneficial to tensile properties of the composites. The highest tensile strength (1454MPa) of the as-extruded 5.1vol.% TiBw/Ti60 composites and the well combination of tensile strength (1364MPa) and elongation (6%) of the as-extruded 3.4vol.% TiBw/Ti60 composites have been obtained at room temperature. In particular, the as-extruded composites also exhibited super-high tensile strength at elevated temperatures (close to 1000MPa at 600°C and 800MPa at 700°C) compared with matrix alloy. Combining analysis of fracture surfaces and microstructure evolution, the better properties can be attributed to the alignment distribution of TiBw along the extrusion direction and the matrix strengthening effects including refinement of grain, the substructure and texture strengthening.