机械合金化及热处理过程中Ti_(33)B_(67)二元系统的结构演变

Structural Evolution of the Ti_(33)B_(67) Binary System During Mechanical Alloying and Subsequent Heat Treatment

采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及粉体粒度仪研究了Ti33B6 7元素混合粉在机械合金化过程中的结构演变、球磨后粉体的颗粒形态与粒度分布以及热处理对粉体结构的影响,讨论了TiB2 机械合金化合成机制。实验结果表明,机械合金化合成TiB2 遵循逐渐扩散反应机制,过程如下:Ti+B→Ti(B) 纳米晶→Ti(B) 非晶→TiB2 纳米晶。球磨2 0h析出TiB2 ,球磨6 0h后完全转变为TiB2 。TiB2 粉体颗粒基本呈球形,具有比较宽的粒径分布,平均粒度d0 5为0 96 4 μm。热处理导致TiB2 粉体晶粒生长,晶粒尺寸增大,晶格畸变程度降低,有序度提高。

The structural evolution of the Ti33B67 element powder in the process of mechanical alloying and subsequent heat treatment was studied using X-ray diffractometer (XRD). The powder morphology and the particle size distribution of the milled powder were analyzed by scanning electron microscopy (SEM) and a particle size analyzer. The synthesis reaction mechanism of TiB2 during mechanical alloying was also discussed. The results show that the gradual diffusion reaction mechanism of TiB2 is followed during milling the Ti33B67 element powder. The reaction is described as follows: Ti + B &rarr Ti(B)nanocrystalline &rarr Ti(B)amorphous &rarr TiB2 nanocrystalline. After the Ti33B67 element powder milled for 20 h, TiB2 is detected by XRD. The Ti33B67 element powder entirely transforms to TiB2 after milling for 60 h. The approximately spherical TiB2 particles are observed. The TiB2 powder has a wide particle size distribution with an average particle size (d0.5) of 0.964 μm. The grain size and lattice ordering degree of TiB2 increase, and the lattice distortion of TiB2 decreases during heat treating the TiB2 powder milled for 60 h.