Description
The relative thermal stability of colloidal silica bonded Al₂O₃ investment casting mold against molten Ti-Al alloy melts was investigated by means of optical microscope, EDS profiles and hardness measurement. Ti-Al alloys with aluminum concentrations less than 30 atomic percent reacted with Al₂O₃ giving the hardening layer, whereas the others have no reaction layer. In the case of the reaction between pure titanium and Al₂O₃ mold, the reaction was affected not only by the stability of Al₂O₃ mold itself but also by the effect of the binder, which was colloidal silica. As aluminum content of Ti-Al alloys increase, the thermal stability of titanium alloys is improved because of chemical compatibility.