Ti-BN粉末冶金原位制备Ti(N)-TiBw复合材料

Microstructure and mechanical properties of Ti(N)-TiBw composites prepared in situ by Ti-BN powder metallurgy

摘要:

本文以纯Ti粉末和BN粉末为原料，采用放电等离子烧结技术(SPS)通过原位反应制备了Ti(N)-TiBw复合材料，研究了退火温度对Ti(N)-TiBw复合材料显微组织演化和力学性能的影响。结果表明:在1000 ℃进行烧结时，Ti与BN发生原位反应生成了TiBw和N固溶复合增强钛基复合材料。TiBw以针状形式呈网络状分布于一次颗粒边界处，随着热处理温度的升高，TiBw的长径比先增大后减小，在1100 ℃时达到最大值。而在1100 ℃以上退火处理时，TiBw逐渐发生粗化，微观形貌从针状变成短棒状，其对基体的钉扎效果明显减弱，Ti基体晶粒尺寸逐渐粗化，TiBw的形貌演变遵循Ostwald熟化机制。随着热处理温度的升高，材料的强度先提高后降低，在1000 ℃达到最大值，为908 MPa。材料强度的提升归因于晶粒细化、TiBw载荷传递和O/N的固溶强化。

Abstract:

In this paper, 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 ℃. 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 ℃. However, when the annealing temperature is above 1100 ℃, 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 ℃. The strength improvement is attributed to grain refinement, TiBw load transfer and O/N solution strengthening.