Microstructure evolution of Ti5Si3 in Cu-Ti-Si alloys

The Cu-Ti-Si alloys containing in-situ formed Ti5Si3are prepared.In order to clarify the Ti5Si3formation processes and its microstructure characteristics,the as-cast and deeply etched Cu-Ti-Si alloys with different compositions and cooling rates were investigated using scanning electron microscopy (SEM),transmission electron microscopy (TEM) and X-ray diffraction (XRD).It is found that the eutectic Ti5Si3phases in Cu-Ti-Si alloys are rod-like with hexagonal cross section which tend to intertwine with each other to form a firm skeleton like a bird nest structure which can make the alloys keep their original shape even after etching off the Cu matrix.In addition,there is Cu in the center of many Ti5Si3rods,resulting in a core-shell structure.With the increase of the cooling rate,Ti5Si3distributes more uniformly,and the diameter of Ti5Si3significantly decreases,with a minimum size of less than 100 nm,while the aspect ratio of Ti5Si3increases.