Research on the related between microstructures and impact toughness of Ti80 alloy

Ti80 alloy with different microstructures, i.e., fully equiaxed α p (FE), equiaxed α p + colony-distributed thick lamellae α l (ECL), and equiaxed α p + disorder-distributed thin lamellae α l (EDL) were tailored to unravel the correlation between microstructure and impact toughness. In particular, the FE and ECL exhibited superior impact toughness (132.5 J/cm 2 and 110.0 J/cm 2 respectively), nearly twice that of EDL (65.0 J/cm 2 ). By investigating the microstructure deformation mechanisms and crack deflection behaviors, we found that equiaxed α p and colony α l in FE or ECL possess superior abilities of plastic deformation and crack deflection, promoting severe deformation of them, tortuous crack paths as well as high energy dissipation. However, EDL exhibited a straight crack path caused by low resistance to crack propagation of disorder-distributed thin α l . Furthermore, the activation of high-density {10 2}<10 1> twins in FE and ECL, effectively released the local stress concentration, facilitated dislocation slip, and refined matrix grains, improving the deformation compatibility. Note that the interstitial β-phase in the α l colony in ECL offered new α/β interfaces and prevented dislocation mobility to a certain extent. This, on one hand, slightly lower the impact toughness as compared to FE, and on the other hand, greatly enhanced the overall strength level. Consequently, ECL demonstrated the best combination of strength and toughness.