Constructing tri-modal microstructure via new three-step heat treatments for improved tensile strength and creep resistance in (TiB+TiC+Y2O3)/α-Ti composite.

In this study, new three-step heat treatments were carried out on the (TiB + TiC + Y 2 O 3)/α-Ti composite to improve the high-temperature performance. The microstructure characterization, tensile properties and creep behaviors of titanium matrix composites before and after heat treatments were systematically studied. Results indicate that the microstructures changed from the basket-weave structure to the tri-mol structure after heat treatments. The cooling process mainly affects the morphology of the secondary α-Ti phases. TiC and Y 2 O 3 undergo extensive spheroidization, while TiB tends to merge and grow. The heat-treated composite exhibited a great improvement in tensile and creep properties, the ultimate tensile strength at 650 °C was increased to 906 MPa with an increase of 10 %, and the creep life 650 °C/230 MPa was improved to 151.7 h with an increase of 91 %. During creep, there are obvious dynamic recrystallization and limited dislocation movement. The three-step heat treatment enhanced the stability of the α/β interface and improved the interface relationship between silicides and titanium matrix. The stable α/β interfaces in transformed β-Ti matrix, fine silicides and spheroidized TiC and Y 2 O 3 particles contributed to the high strengthening efficiency. • The tri-modal microstructure was achieved in (TiB + TiC + Y 2 O 3)/α-Ti composite. • The reasons for the enhanced tensile and creep properties by the three-step heat treatment were analyzed. • The characteristics of reinforcements and precipitated silicides after creep were investigated. • Dynamic recrystallization behavior promoted by reinforcements were discussed. • The interfaces between matrix, silicide and reinforcements were analyzed by TEM. [ABSTRACT FROM AUTHOR]