原位自生Ti-TiBw复合材料中TiBw粗化机理研究

Study on coarsening mechanism of TiBw in in-situ Ti-TiBw composites

以纯Ti粉和TiB_(2)粉为原料,采用放电等离子烧结技术制备原位自生Ti-TiBw复合材料,系统研究了热处理条件对Ti-TiBw复合材料组织演变及力学性能的影响。结果表明:Ti和TiB_(2)在1000℃烧结后原位反应生成了Ti-TiBw复合材料,TiBw主要以团簇状分布于基体的一次颗粒边界(PPBs)处,少量以针状分布于晶界及晶内。热处理结果表明,温度是TiBw发生粗化的主导因素,且TiBw粗化发生在升温阶段,粗化温度为1200℃。其粗化行为遵循Ostwald熟化机制:为使体系自由能降低,溶质B原子从小尺寸TiBw周围向大尺寸TiBw周围进行扩散并沉积,使得TiBw数量减少,对基体的割裂程度减弱,因此材料延性提高。

The in-situ autogenerated Ti-TiBw composites were prepared by spark plasma sintering using pure Ti powder and TiB_(2)powder as raw materials.The effect of heat treatment conditions on the microstructure evolution and mechanical properties of Ti-TiBw composites were systematically studied.The results show that Ti-TiBw composites are synthesized in situ after sintering Ti and TiB_(2)at 1000℃.TiBw is mainly distributed in clusters at the primary particle boundary of the matrix,and a small amount of TiBw is distributed in the grain boundary and ingrain.The heat treatment results show that temperature is the dominant factor for TiBw coarsening,and TiBw coarsening occurs in the heating stage,and the coarsening temperature is 1200℃.The coarsening behavior follows the Ostwald ripening mechanism:To reduce the free energy of the system,solute B atoms diffused and deposited around small-size TiBw to large-size TiBw,reducing the amount of TiBw and weakening the degree of cleavage to the matrix,thus improving the ductility of the material.