单相组织TWIP钢的扩孔性研究  

Hole expansion property of TWIP steel with single-phase microstructure

作　　者：姜英花[1,2] 谢春乾 邝霜 

机构地区：[1]首钢技术研究院薄板研究所,北京100043 [2]绿色可循环钢铁流程北京市重点实验室,北京100043

出　　处：《材料科学与工艺》2017年第6期61-65,共5页Materials Science and Technology

摘　　要：超高强钢的扩孔性能是冲压成形的重要性质.为评价980 MPa TWIP钢的扩孔性能,本文以单相铁素体IF钢和980 MPa双相钢作为参考材料,用扫描电镜观察了3个钢种的微观组织,并对3个钢种进行了拉伸实验和扩孔实验,采用背散射电子衍射(EBSD)技术分析了拉伸后和扩孔实验后TWIP钢的微观组织.实验结果表明:拉伸前TWIP钢呈现类似于IF钢均匀的单相奥氏体组织,而拉伸后TWIP钢呈现类似于DP钢不均匀的硬质变形孪晶奥氏体和软质奥氏体;扩孔后TWIP钢的开裂位置集中在奥氏体和变形孪晶奥氏体界面;虽然TWIP钢显现出更大的均匀伸长率和加工硬化,但扩孔率明显小于IF钢.TWIP钢扩孔率增加源于早期孪晶诱发塑性(TWIP效应)导致的均匀变形.同时,这种变形机制导致组织中的硬质变形孪晶奥氏体,硬质变形孪晶奥氏体与软质奥氏体匹配(类似于双相钢中马氏体铁素体匹配)将恶化局部变形,阻碍扩孔性能进一步提升.Hole expansion property is an important property for ultra high strength steel（ UHSS） sheets for press forming. To evaluate the hole expansion property of 980 MPa TWIP steel,a fully ferritic IF steel and a980 MPa DP steel were used as model materials in the present study. The microstructures of the three steels were observed by scanning electron microscopy（ SEM） and electron back-scatter diffraction（ EBSD） before and after tensile tests and hole expansion tests,respectively. After tensile tests and hole expansion tests. The as-received TWIP steel exhibits a structure of homogeneous single austenite,identical to IF steel,whereas shows a mixed structure of. hard austenite with deformation twins and soft austenite after tensile deformation,similar to DP steel. The cracks in TWIP steel after hole expansion tests locate atthe interface between austenite and twin austenite. Although TWIP steel showed a larger elongation and work hardening capacity,its hole expansion rate was less than IF steel. The enhanced hole expansion rate of TWIP steel can be attributed to the uniform deformation caused by early twinning induced plasticity（ TWIP effect）. Meanwhile,this deformation mechanism leads to the formation of hard austenite with deformation twins in the steel. The hard austenite with deformation twins and soft austenite will deteriorate the local deformation,hindering the further enhancement in the hole expansion property.

关 键 词：扩孔性 组织 局部变形 裂缝 变形孪晶 

分 类 号：TG142.1[一般工业技术—材料科学与工程]