Abstract
This paper reports the micro structure and the elemental maps of some internal defects in the titanium casting, formed by reactions with the investment inclusion.The defect, without a hole or with an irregular or a circular hole, accompanied the oxygenstabilized α phase and the acicular structure corresponding to the oxygen content distribution.Silicon and aluminium, occasionally phosphorus and magnesium, existed in and around the defect;the micro structure was similar to the layered structure of the casting surface.The defect, especially the oxygen-stabilized α phase, played an important role in the source of crack initiation.Probably, some of the observed cracks were formed through the plastic bending deformation of the casting, and the others, through the cooling process of the casting.
