超细晶铁素体钢的力学性能及成形性能研究

Study of mechanical properties and forming properties of ultra-fine grain ferrite steels

采用形变强化铁素体相变超细晶轧制工艺,获得了750MPa级超细晶铁素体钢板,其超细晶铁素体体积比高达93%,晶粒尺寸仅为1μm,并具有优异的成形性能。对超细晶铁素体钢组织的精细分析发现,因铁素体晶界随晶粒超细化而减薄,使得其晶界对材料的力学性能具有双重影响,一方面,屈服强度随着晶界总长度的增加而提高;另一方面,又因晶界减薄而降低。研究表明,超细晶铁素体钢的组织性能关系虽然与霍尔-佩奇关系相吻合,但存在较大偏差,主要表现为斜率显著下降。文章对斜率下降的原因进行了机理分析。

A kind of ferrite steel plate with ultra-fine grain structure and prominent tensile strength about 750MPa was developed by using deformation enhanced ferrite transformation ultra-fine grain rolling technology. The steel plate＇s volume percent of ultra fine ferrite is 93% and grain size of ultra-fine grain ferrite is only 1μm, thus enhances the forming properties remarkably. The exact analyzing discovered that ultra-fine grain ferrite steel＇s boundaries is thinning as grain refining, the effect of grain boundaries on mechanical property present in two aspects：With increasing the grain boundaries total length, the yield strength increase;On the other hand, the yield strength is reducing as grain boundaries thinning. The research results showed that the ultra-fine grain ferrite steel mierostrueture and properties relation matches Hall-Patch relationship, but there is big deviation. The deviation is the slope of the Hall-Petch decrease obviously. Furthermore, the mechanics analysis about the reason of slope decreasing has been made.