Crack Formation Analysis of ZTA7 Investment Casting

Through the analysis of surface cracks of ZTA7 titanium investment casting,the causes of surface cracks on titanium alloy casting without the influence of surface α contamination layer were determined. The results show that when the ZTA7 casting is repair welded, the microstructure of the substrate is changed and needle α phase appears due to the thermal effect during repair welding, the oxygen diffuses to titanium alloy and oxygen-rich diffusion layer is formed.Therefore, the plastic toughness of the heat-affected zone is greatly reduced, and under the action of welding stress, cold welding cracks are formed.