Establishment Method for Hard-Alpha Defect Distribution Curve of Titanium Alloy of Aero-Engine Life-Limited Parts Considering the Effect of Hot Processing

Manufacturing defects in life-limited parts of aero-engines, such as hard alpha inclusions and machining scratches, seriously threaten the safety of the aero-engine. The probabilistic failure risk assessment method has been developed to quantitatively assess the impact of material and manufacturing defects on engine failure risk by assuming a material initial defects distribution curve. The distribution of melting defects hard alpha is the core input to the probabilistic failure risk analysis, which is significantly affected by hot processing, such as forging deformation ratio, deformation rate, and deformation temperature. However, limited research has been conducted to investigate the impact of hot working on defect distribution curves. Hence, this paper proposed a method for correcting titanium alloys’ internal hard alpha defect distribution curve. Firstly, based on the experimental data of the artificial hard-alpha defects, the constitutive model is established for the TiN material. Then, the finite element software DEFORM was used to simulate the thermal deformation model of the bar forging and hard-alpha inclusion deformation. Afterward, the thermal deformation law of the hard-alpha inclusion with forging was obtained. Finally, a hard-alpha defect deformation model is established based on the defect deformation law, and the correction line of the hard-alpha defect distribution curve is obtained. The error between the hard-alpha defect deformation model and the artificial preset defect forging test is less than 50%. The deformation model will be applied to correct the critical defect data of domestic titanium alloy materials and then establish the defect distribution curve that reflects domestic materials’ processing level. The correction curve can support the airworthiness forensics of domestic autonomous models.