High impact toughness of CT20 alloy induced by multi-factor coupling.

• The CT20 alloy with bimodal microstructure shows excellent impact toughness. • The microstructure with stronger twinning ability can absorb higher crack initiation energy. • Dynamic impact load may induce phase transformation in CT20 alloy. • The higher impact toughness is caused by the coupling of multiple factors. • Especially, micro-voids of the CT20 alloy with bimodal microstructure tend to initiate in α s rather than α p. Impact deformation behaviors of CT20 alloy with lamellar microstructure (LM), equiaxed microstructure (EM) and bimodal microstructure (BM) at room temperature were systematically investigated in this study. The experimental results indicated the excellent mechanical properties of CT20 alloy with BM under dynamic load. The impact toughness of BM specimen (∼118 J/cm²) is ∼17.5 % higher than that of LM specimen and ∼33.8 % higher than that of EM specimen. The impact energy of EM specimen is the lowest due to the relatively simple equiaxed microstructure. LM specimen can absorb the highest crack initiation energy due to the best twinning ability. The highest impact toughness of BM specimen is induced by multi-factor coupling during impact deformation. Finer initial equivalent grain size, smaller lamellar thickness, lamellar induces twinning, finer twins, crack propagation path, and interaction between twins and β lamellar are all factors affecting impact toughness. [Display omitted] [ABSTRACT FROM AUTHOR]