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 degrees 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.