Modulation of microstructure and improvement in the mechanical properties of TiBw/Ti65 composites by rolling at different temperatures

The effect of rolling temperature on microstructure evolution and mechanical properties of as-sintered TiBw/ Ti65 composites was systematically investigated. The results showed that at 900 degrees C (in the low alpha + beta phase region), the matrix microstructure primarily exhibited a deformation structure. At 1000 degrees C (in the high alpha + beta phase region), a bimodal structure was observed, and at 1100 degrees C (in the beta phase region), a basket-weave structure emerged. Additionally, silicides precipitated at 900 degrees C were fine but grew and coarsened at 1000 degrees C, eventually dissolving almost completely into the matrix at 1100 degrees C. This behavior is attributed to the varying solubility of silicides in the alpha and beta phases. With increasing rolling temperature, the dynamic recrystallization (DRX) mechanism within the TiBw/Ti65 composites transitioned from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX). Rolling significantly enhanced the mechanical properties of the composites. The HR-900 composite exhibited the optimal strength-plasticity combination at room temperature, achieving an ultimate tensile strength (UTS) of 1415 +/- 21 MPa and elongation (EL) of 6.2 +/- 2.7%, mainly due to grain refinement and work hardening. Conversely, the HR-1100 composite demonstrated superior hightemperature mechanical performance, showing improvements of 37.18%, 27.05%, and 9.59% at 963 MPa (650 degrees C), 789 MPa (700 degrees C), and 560 MPa (750 degrees C), respectively, compared to those of the as-sintered materials. The strengthening mechanisms were fine-grain strengthening, dislocation strengthening, and load transfer strengthening of the as-rolled composites, and the primary strengthening mechanism shifts from dislocation to fine-grain strengthening as the rolling temperature increases.