Preparation of Laminated Titanium Matrix Composites with High Strength and Plasticity via Regulating Heat Treatment Processes

In order to achieve a balance between the strength and ductility of titanium matrix composites (TMCs), a spray deposition method was employed to deposit carbon nanotubes (CNTs) onto the surface of Ti foil. Subsequently, spark plasma sintering (SPS) at 850 degrees C and an additional 1 h heat treatment at 880 degrees C were utilized to fabricate two laminated composites of different composition, namely, CNTs/Ti (SPS) and in situ TiC/Ti (SPS+HT). The microstructure evolution, mechanical properties, and strengthening and fracture mechanisms of laminated composites were systematically studied. The results revealed that after sintering at 850 degrees C, the reaction between CNTs and the titanium matrix was limited. However, after a 1 h heat treatment at 880 degrees C, CNTs were completely transformed into TiC, while the titanium matrix remained alpha phase without undergoing phase transformation. Through rolling and annealing, TiC particles were refined to 500 nm and exhibited a flattened shape. The in situ TiC/Ti layered composite material exhibited a tensile strength (UTS) of 491.51 MPa, which was a 29.63% improvement compared to pure titanium (379.16 MPa), and significantly higher than the UTS of CNTs/Ti samples (419.65 MPa). The primary strengthening mechanism was load transfer strengthening. The elongation (EL) remained at 26.59%, slightly lower than pure titanium (29.15%) and CNTs/Ti samples (27.51%). This can be attributed to the increased connectivity of the matrix achieved through rolling, which enhanced the ability to passivate cracks and prolonged the crack propagation path. This study presents a method for preparing laminated titanium matrix composites with both strength and ductility by controlling the heat treatment process.