Search

Abstract: By the analysis of true stress–strain curves and the observation of microstructures at different deformation stages, the dynamic recrystallization (DRX) of a Nb micro-alloyed steel and a plain carbon steel is studied, and the critical stress and critical strain are determined under different deformation conditions. By the method of stress relaxation, the post-dynamic recrystallization of two steels is studied. The energy to induce recrystallization of austenite of Nb steel is higher than that of the plain carbon steel. The critical stress of DRX for Nb steel is higher than that for the carbon steel. The apparent activation energy of static recrystallization Q srx of Nb steel and the plain carbon steel is 318 and 231kJ/mol, respectively. It is obvious that Nb in solid solution increases the value of apparent activation energy (Q srx) dramatically. The precipitation and recrystallization are in competition because of stored deformation energy. The work shows that the ratios of ɛ p to ɛ c and that of ɛ * to ɛ c are 1.6 and 2.2, respectively, for the steels. [Copyright &y& Elsevier]

Abstract: An ultrahigh-carbon steel containing 1.6wt.% carbon (UHCS-1.6C) was processed to obtain ultrafine spheroidized ferrite, pearlite and tempered martensite, respectively. The tensile properties of these structures were evaluated at room temperature. The ultimate tensile strengths of UHCS-1.6C ranged from 930 to 1570MPa, elongations to failure from 4.4 to 19%, and yield ratios from 0.65 to 0.92. The fracture mechanisms of these structures were clarified based on an examination to the fracture surfaces. The present results indicate that ultrahigh-carbon steels can be easily processed to achieve unique microstructures and properties. [Copyright &y& Elsevier]