带状组织对冷轧双相钢DP780力学性能的影响  

Effect of banded structure on mechanical properties of cold-rolled dual phase steel DP780

作　　者：薛仁杰 董伊康 马子洋 曹晓恩 李志昂 Xue Renjie;Dong Yikang;Ma Ziyang;Cao Xiao'en;Li Zhi'ang(Automotive Materials R&D Center,Materials Technology Research Institute,HBIS Group,Shijiazhuang Hebei 052165,China;Technology Center,Hansteel Company,HBIS Group,Handan Hebei 056015,China)

机构地区：[1]河钢材料技术研究院汽车材料研发中心,河北石家庄052165 [2]河钢集团邯钢公司技术中心,河北邯郸056015

出　　处：《金属热处理》2024年第12期191-197,共7页Heat Treatment of Metals

基　　金：河北省科技研发平台建设专项(23561006D)。

摘　　要：为了研究冷轧双相钢DP780中带状组织元素偏析行为及其对力学性能的影响,采用OM、SEM、EMPA、EBSD等技术方法对带状组织形态及元素分布特点、拉伸性能及拉伸过程组织形态变化、断口机制等进行了表征分析。研究结果显示,由于凝固过程溶质再分配C、Mn、Al与Si元素的宏观偏析导致带状组织的形成,带状组织多位于板厚1/2和1/4处,平行于轧向分布,晶粒尺寸分布明显不均匀,带状组织小角度晶界密度明显高于等轴组织。拉伸过程性能及组织形态变化表明,经过10%拉伸预变形后,带状组织试样组织纤维化更明显,增加了变形过程位错移动阻力,使得材料强度提升;带状组织也易造成位错塞积与晶格畸变,恶化材料变形能力;带状组织降低了基体组织的协调变形能力,导致材料各向异性突出。断口形貌观察发现,带状组织试样初始裂纹在M/F相界面处萌生,断裂时在带状组织M/F界面形成撕裂脊,撕裂脊位置和尺寸与带状组织相吻合;撕裂脊之间为塑性变形能力较差的马氏体带状区域,而M/F界面铁素体一侧发生显著塑性变形;等轴组织试样呈现轴向均匀变形特点,断裂塑性更优。In order to study the segregation behavior of elements in the banded structure of cold-rolled duplex steel DP780 and its effect on mechanical properties,OM,SEM,EMPA,EBSD and other methods were used to characterize and analyze the morphology and element distribution characteristics of the banded structure,tensile properties and microstructure change during the tensile process,fracture mechanism,and so on.The research results show that the macroscopic segregation formed by redistribution of C,Mn,Al and Si solute elements during the solidification process leads to the formation of banded structure,which is mostly distributed parallel to the rolling direction at 1/2 and 1/4 of the plate thickness,the grain size distribution is obviously nonuniform,and the small angle grain boundary density of the banded structure is significantly higher than that of the equiaxed structure.Meanwhile,the properties and microstructure change in tensile process indicate that after 10%tensile pre-deformation,the fibrosis is more obvious in the banded structure specimen,increasing the resistance of dislocation movement during the deformation process and improving the strength.The banded structure can also cause dislocation pile-up and lattice distortion,deteriorating the ability to deform.The banded structure reduces the coordinated deformation ability of the matrix structure,resulting in prominent anisotropy.Further,the observation of fracture morphology shows that the initial crack initiation occurs at the M/F phase interface,and a tear ridge is formed at the M/F interface during fracture,while the location and size of the tear ridge are consistent with that of the banded structure.There is a martensite band region with poor plastic deformation ability between the tear ridges,and the ferrite side of the M/F interface has significant plastic deformation;the specimen with equiaxed structure exhibits uniform axial deformation and better fracture plasticity.

关 键 词：带状组织 双相钢DP780 断裂机制 宏观偏析 协调变形 

分 类 号：TG113.25[金属学及工艺—物理冶金]