Microstructure and Mechanical Properties of Ti(N)-TiBw Composites Prepared in situ by Ti-BN Powder Metallurgy

Ti(N)-TiBw composites were prepared by spark plasma sintering (SPS) with pure Ti powder and BN powder as raw materials. The effect of annealing temperature on microstructure evolution and mechanical properties of Ti(N)-TiBw composites was studied. Results show that Ti and BN react in situ to form dense TiBw and N solution strengthened titanium matrix composites when sintered at 1000 degrees C. TiBw is distributed in the primary particle boundary in the form of needle like network. With the increase of heat treatment temperature, the aspect ratio of TiBw first increases and then decreases, reaching the maximum at 1100 degrees C. However, when the annealing temperature is above 1100 degrees C, TiBw coarsens gradually, and the microstructure changes from needle shape to short rod shape. The pinning effect of TiBw on the matrix is obviously weakened, and the grain size of Ti matrix coarsens gradually. The morphology evolution of TiBw follows Ostwald ripening mechanism. As the heat treatment temperature increases, the ultimate tensile strength of the composites first increases and then decreases, reaching a maximum value of 908 MPa at 1000 degrees C. The strength improvement is attributed to grain refinement, TiBw load transfer and O/N solution strengthening.

Automated summary

Ti(N)-TiBw composites were prepared by spark plasma sintering (SPS) and the effect of annealing temperature on their microstructure and mechanical properties was investigated. The results showed that dense composites with high tensile strength could be obtained at 1000 degrees C.