摘要
随着双碳战略与汽车轻量化战略的实施,占社会总碳排放18%的交通领域需加快实现绿色低碳转型,这极大地促进了低排放、低成本、高性能先进高强钢的发展。δ-TRIP钢具有密度低、焊接性好与强塑性较高等优点,但由于组织中存在粗大的条带状δ铁素体,使其强度与伸长率低于一般中锰钢,且粗大δ铁素体界面往往成为裂纹形核与扩展的通道,表层粗大δ铁素体对钢的塑性影响更大。为了对表层粗大δ铁素体进行改性以提高钢的塑性,在退火过程利用空气中的氧气与氮气共同作用,在晶界析出AlN第二相粒子并将其作为再结晶形核点,促进δ铁素体等轴化与细化过程。在无气氛保护的箱式炉中600℃等温不同时间进行试验,研究δ-TRIP钢组织演变规律及强塑机制,并采用光学显微镜、扫描电镜、XRD与单向拉伸对其组织性能进行了表征分析。研究结果表明,短时等温组织主要为条带状δ铁素体与少量等轴α铁素体、马氏体及奥氏体,表层δ铁素体发生等轴化;随着等温时间的延长,组织中的马氏体逐渐转变为奥氏体,且表层δ铁素体等轴化向芯部渗透。试验钢的强度总体上随等温时间的延长呈下降趋势,在前期降幅较大;而伸长率随等温时间的延长先上升后下降。在600℃等温12 h条件下,由于TRIP效应与表层δ铁素体等轴化综合作用,获得相对优异的力学性能,此时屈服强度、抗拉强度与伸长率A50分别达504.5 MPa、623.4 MPa与22.8%。
With the implementation of the carbon reduction strategy and the lightweight strategy of automobiles,the transportation field,which accounts for 18%of the total carbon emissions of society,needs to accelerate the green and low-carbon transition.Thus,it will greatly promote the development of advanced high-strength steel with low emissions,low cost and excellent mechanical properties.δ-TRIP steel has the advantages of low density,good weldability,and high strength plasticity,but the presence of coarse bandδ-ferrite makes its strength and elongation lower than traditional medium manganese steel,and the interfaces of the coarseδ-ferrites often serve as a channel for crack nucleation and propagation.Even worse,coarse surface layerδ-ferrite has a greater impact on the plasticity of steel.In order to modification of coarse surface layerδ-ferrite to improve the plasticity of steel,the synthetical effect of oxygen and nitrogen in the air was utilized during annealing to facilitate the precipitation of AlN second phase particles at grain boundaries,which were acted as nucleation points for recrystallization to promote equiaxialization and refinement ofδ-ferrite.The isothermal experiments for different times in a 600℃box furnace without atmosphere protection were conducted to explore the microstructure evolution and strength plasticity mechanism ofδ-TRIP steel.The microstructures and mechanical properties after the experiment were characterized with optical microscopy,scanning electron microscopy,XRD,and uniaxial tensile testing.The results show that the microstructures of the specimens isothermal for a short time are mainly composed of bandδ-ferrite,a small amount of equiaxedα-ferrite,martensite and austenite,and equiaxation of ferrite is only occurred in the surficial layerδ-ferrite.As the isothermal time increases,the martensite in the microstructure gradually transforms into austenite,and the equiaxation ofδ-ferrite also occurs in the sub-surfaces and cores.The strength of the experimental steel generally presents a decreasing trend with the increasement of the isothermal time,with a significant decrease in the early stage.However,the elongation first increases and then decreases with the extension of isothermal time.Due to the comprehensive effect between the TRIP effect and the equiaxation of surficialδ-ferrite,the sample at isothermal temperature of 600℃for 12 h has a relatively excellent mechanical properties with yield strength of 504.5 MPa,tensile strength of 623.4 MPa and elongation at 50 mm gauge lengths of 22.8%.
作者
余浩
杨璐
潘红波
刘伟明
魏海莲
刘永刚
谷海容
YU Hao;YANG Lu;PAN Hongbo;LIU Weiming;WEI Hailian;LIU Yonggang;GU Hairong(Key Laboratory of Metallurgical Emission Reduction and Resources Recycling of Ministry of Education,Anhui University of Technology,Maanshan 243002,Anhui,China;Anhui Province Key Laboratory of Low Carbon Metallurgy and Solid Waste Resource Utilization,Anhui University of Technology,Ma'anshan 243002,Anhui,China;School of Materials Science and Engineering,Anhui University of Technology,Maanshan 243032,Anhui,China;Technology Center,Maanshan lron and Steel Co.,Ltd.,Maanshan 243002,Anhui,China)
出处
《钢铁》
CAS
CSCD
北大核心
2024年第11期173-182,共10页
Iron and Steel
基金
国家自然科学基金资助项目(U1860105,51774006)
安徽省重点研发计划资助项目(202304a05020026)。
关键词
Δ铁素体
等轴化
中锰钢
第二相粒子
强塑机制
δ-ferrite
equiaxation
medium manganese steel
second phase particle
strength plasticity mechanism
作者简介
余浩(1997—),男,硕士生,E-mail:2493216003@qq.com;通信作者:潘红波(1978—),男,博士,教授,E-mail:panhb718@163.com。
