Influence of trace boron on the morphology of titanium carbide in an Al-Ti-C-B master alloy

The influence of trace B (boron) element on the morphology of TiC crystals in an Al-Ti-C-B master alloy prepared by a melt reaction method has been investigated in this paper. The morphology and chemical composition of TiC crystals are characterized from X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersion spectroscopy (EDS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analyses. It is found that both TiC hexagonal platelet and TiC polyhedron have formed in the Al-Ti-C-B master alloy. Furthermore, a trace amount of B element is found in TiC hexagonal platelets evidenced by the EDS spectrum. However, the SAED pattern confirms that the crystal structure of TiC has not changed. The formation and growth mechanism of the TiC hexagonal platelet have been discussed. It is considered that the trace B element in the aluminum melt promotes the transformation of TiC from polyhedron to hexagonal platelet at the initial growth stage.