Fracture behavior of lamellar structure in Ti-48Al-2Mn-2Nb alloy produced by centrifugal spray deposition

The effects of lamellar structure on deformation and fracture behavior in a Ti-48Al-2Mn-2Nb alloy produced by centrifugal spray deposition(CSD) were investigated. The deformation and fracture of samples after tensile and compressive tests were examined in a scanning electron microscope (SEM). The in situ tensile testing was further carried out in a SEM and the crack growth path of samples was observed. The result shows that there is a remarkable effect of lamellar structure of CSD TiAl alloy on its deformation and fracture process. Especially, the main crack extension is dependent on the lamellar direction relative to tensile loading axis. SEM observations indicate that there is a shielding toughening effect of lamellar structure on fracture in CSD samples, such as, crack deflection, crack path tortuousity, and crack branching, etc. Moreover, the crack growth path shows that the main crack grows tortuously and uncontinuously by ligaments bridging many microcracks in front of crack tip. The effect mechanism of microstructure on deformation and fracture process is discussed.