Strengthen and Toughen the Low‐Alloyed Steel by Direct Tempforming

Improving strength without sacrificing toughness is a permanent request for the development of advanced engineering materials. Herein, a novel energy‐saving strategy is developed to obtain strong but tough low‐alloyed steels. A medium‐carbon steel (42CrMo) is used for demonstration. Warm deformation (tempforming) is applied to the hot‐rolled and air‐cooled 42CrMo steel. After tempforming, the microstructure consists of nano‐sized carbides and highly textured ultrafine grains. The tensile strength of the tempformed steels can reach 1.2 GPa, while the impact toughness is higher than 100 J even at temperatures as low as −80 °C, which are one order of magnitude higher than the counterpart steel after tempering. The present work sheds light on the design and fabrication of high‐performance engineering steels with an excellent combination of strength and toughness.