Mechanical behavior and microstructural evolution of nanostructured bainite under high-strain rate deformation by Hopkinson bar

To explore the mechanical behavior and microstructure evolution of nanostructured bainite under deformation at high strain rates (>10(3) s(-1)), split Hopkinson pressure bar experiments were conducted. It was found that nanometer-sized twinning occurred in both blocky austenite and film austenite. In the former case, the intersections of different twin variants brought about strain-induced alpha'-martensite, while in the latter case, the lamellar twinned structures were occasionally accompanied by a small amount of epsilon martensite. It is concluded that twinning occurs first in blocky austenite, enhancing the initial work-hardening; subsequent twinning takes place in film austenite, promoting further straining. (C) 2015 Elsevier Ltd. All rights reserved.