Growth mechanism of in situ TiB whiskers in spark plasma sintered TiB/Ti metal matrix composites

In situ TiB whisker reinforced Ti-4.0Fe-7.3Mo matrix composites have been fabricated by spark plasma sintering (SPS). The microstructure of the in situ TiB whiskers and interfacial structures in the composites were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM). The interfaces between in situ TiB and the Ti matrix are clean and faceted along the (100)_TiB plane. However, small lateral growth steps are observed along the (101) and (101) planes of TiB. Because of the characteristics of the TiB crystal structure, the growing velocity of the (100)_TiB plane along the [010]_TiB direction is much faster than that of the [001]_TiB direction, which leads to TiB growth as a whisker shape along the [010]_TiB direction with a hexagonal transverse section. The growth mechanism of TiB whiskers is a stacking process of the (100)_TiB plane.