Ballistic limits and failure patterns of TiAl alloy plates in particle impact

• Particle impact tests were conducted on TiAl alloys with four different microstructures. • Crack formation was visualized using high-speed camera imaging. • 3D profilometry and SEM observations were used to analyze fracture surface morphology. • Strain rate sensitivity and failure behavior were characterized using SHPB test data. • Finite element model using the Johnson–Cook equations predicted residual velocities. TiAl alloys have been gradually adopted for low-pressure turbine blades in aircraft engines due to their heat resistance and low density. However, TiAl alloys, which are quasi-brittle materials, may be severely damaged by impact with debris generated from the forward stages of the engine. To prevent accidents caused by such damage, it is important to develop an evaluation method for particle impact on TiAl alloys. In this study, particle impact tests were conducted on TiAl alloys. The fracture formation process was captured using a high-speed camera, and the shape of the fracture surface was analyzed using a three-dimensional profilometer. The proportions of inter-lamellar and trans -lamellar fractures, as well as the crack tortuosity, were calculated from the scanning electron microscopy images. To examine the applicability of existing evaluation models, the Johnson–Cook constitutive model and fracture model, with material constants obtained from Split Hopkinson Pressure Bar tests, were applied. The validity of the model was then verified by comparing the residual velocity, fracture formation process, and fracture surface morphology. As a result, it was suggested that the ballistic limit may increase with increasing crack tortuosity. It was found that residual velocity can potentially be evaluated using the Johnson–Cook constitutive and fracture models.