Effect of retained austenite on the fracture behavior of a novel press-hardened steel
作者机构：State Key Laboratory of Rolling and AutomationNortheastern UniversityShenyang 110819China China Science LaboratoryGeneral Motors Global Research&DevelopmentShanghai 201206China
出 版 物：《Journal of Materials Science & Technology》 (材料科学技术（英文版）)
年 卷 期：2023年第135卷第4期
页 面：34-45页
核心收录：
学科分类：08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0802[工学-机械工程]
基 金：The work was financially supported by the National Natural Science Foundation of China(Nos.52111530093 52011530032 and 52071066).
主 题：Press-hardened steel Retained austenite Tensile property Bending toughness Crack initiation
摘 要：Tensile and bending properties are two critical attributes of press hardened steels(PHSs)for automotive body structural components.However,the research on these properties of PHSs with retained austenite(RA),which is introduced to improve the mechanical properties,has not been well reported.In this study,the effect of RA on the quasi-static uniaxial tensile and three-point bending behaviors has been systematically investigated for a newly developed Cr and Si alloyed PHS.RA with various degrees of mechanical stabilities was obtained by tuning the auto-tempering of martensite through the control of the die contact pressure during the press hardening process.Mechanically stable RA provides the optimal combination of tensile and bending performance,while the PHS with RA of poor mechanical stability has a deteriorated bending toughness as manifested by a reduction of bending angle from approximately 61.6°to56.8°.However,itstensileproperties,incontrast,arethebestintermsof theproductofulti-mate tensile strength and total elongation(15.9 GPa%).This is mainly attributed to the unstable RA on the outermost surface of the bending sample.The unstable RA can easily transform into brittle martensite under local plane strain and strain gradient conditions in the bending test compared with uniaxial stress in the tensile test,promoting crack initiation and propagation.Furthermore,the effect of martensitic auto-tempering or contact pressure on the quantity and stability of RA are also discussed.This study would provide a useful reference to guide hot stamping process optimization for the newly developed Cr and Si-containing press-hardened steel.
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