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通过成分工艺优化,在传统冷轧铁素体和马氏体双相钢DP780的显微组织上引入了一定体积分数的残余奥氏体,研究了冷轧退火工艺参数对双相钢DP780的显微组织和力学性能的影响。通过调整连续退火工艺来控制显微组织中一次铁素体、二次铁素体、马氏体、残余奥氏体的比例、尺寸、形貌、分布,同时获得了连退工艺参数-显微组织-力学性能的本质关系。结果表明,通过在传统冷轧铁素体和马氏体双相钢的组织上引入了体积分数为5%~7%的残余奥氏体,不仅可以获得[ReL/Rm≤0.5]的超低屈强比型冷轧DP780,也改善了成型性能。 相似文献
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实验室设计了Nb-Cr-RE系微碳DP钢,利用扫描电镜以及拉伸试验机,观察与分析了退火温度对微碳DP钢组织与性能的影响.结果表明:微碳DP钢退火板主要由铁素体及其晶界上附着的细小马氏体所构成;随退火温度的上升,DP钢的抗拉强度先升后降,屈服强度逐渐降低,伸长率先增加后降低;铁素体再结晶越充分,晶粒尺寸分布越均匀,等轴化越明显,DP钢屈服强度越小,伸长率越高;另外高温退火时的较大尺寸短棒状碳化物会明显恶化伸长率. 相似文献
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通过Gleeble-1500热模拟压缩试验,借助光学显微镜、扫描电镜、X射线衍射及拉伸试验等,研究一种低碳Mn-Si钢在基于热轧动态相变的热轧TRIP钢工艺和基于贝氏体等温处理工艺下的组织与力学性能,比较了通过两种工艺获得的不同复相组织状态对材料的加工硬化能力的影响.结果表明:实验钢在基于动态相变的热轧TRIP钢工艺下获得了以细晶铁素体为基体和贝氏体、残余奥氏体组成的复相组织,而在基于贝氏体等温处理工艺下得到了以板条贝氏体为基体和残余奥氏体组成的复相组织,前者中残余奥氏体含量较高且其碳含量也较高.实验钢具有以板条贝氏体为基体的复相组织时屈服强度和抗拉强度较高;但由于残余奥氏体稳定性较差,实验钢的加工硬化能力较弱,导致其均匀延伸率和总延伸率较小. 相似文献
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构建了一种新的非饱和流动曲线模型,即LOGSE模型,研究了Combined Swift-Hockett-Sherby模型、Hockett-Sherby模型、LOGSE模型、Ghosh模型和Swift模型对汽车板DP用钢的适用性。以汽车板用钢DP590、DP780、DP980、DP1180及DP600材料为研究对象,以单向拉伸试验数据为拟合目标,采用不同的流动曲线模型对均匀塑性变形阶段的真应力-塑性应变曲线进行拟合,从均方根、相关系数、屈服强度及均匀应变四个方面分析拟合精度,可以发现模型的拟合精度都很高。而在大应变范围内,模型差异逐渐变大,但存在规律性。以DP600单向拉伸试验为拟合目标,比较分析大塑性变形阶段的模型曲线与液压胀形试验曲线的差异,结果显示,LOGSE模型计算精度最高,其次为Hockett-Sherby模型和Combined S-H模型,Ghosh模型和Swift模型计算精度最差,最后给出了国内常用的DP590、DP780、DP980、DP1180汽车板DP用钢在大塑性变形阶段的变化曲线,为冲压或辊压成形前期成形仿真提供参考。 相似文献
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采用动态拉伸试验方法对双相高强钢B340-590DP的动态变形行为进行了研究,试验的应变速率为0.003~530s-1,得到了不同应变速率下的应力-应变曲线。并对不同应变速率下的材料伸长率、抗拉强度以及显微组织进行了分析。试验结果显示,随着材料应变速率的升高,双相钢材料的流变应力、屈服强度和抗拉强度均随之升高,双相钢材料在中等应变速率范围内的伸长率和成形性最好。双相钢的显微组织分析表明,双相钢变形主要发生在铁素体相内,铁素体晶粒沿着高速拉伸方向被拉长。 相似文献
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为了研究DP980双相钢在不同应变速率下的微观组织特征及变形机制。通过室温准静态拉伸(0.001、0.01和0.1 s-1)和分离式霍普金森拉杆高应变速率拉伸实验(1 156、2 861和3721 s-1)进行了力学性能评测。借助OM和SEM对变形断口附近的材料的显微组织微观形貌进行了系统表征和分析。结果表明:DP980双相钢的屈服强度、抗拉强度和断后伸长率随着应变速率的提高而不断提升,表现出明显的塑性和强度的双增现象。不同应变速率下DP980双相钢的断裂方式均为韧性断裂,但在高应变速率下韧窝分布更为均匀,且大尺寸韧窝数量以及韧窝深度均大幅增加。在高应变速率下除了在铁素体和马氏体相界面发生脱粘现象外,马氏体基体内部出现了开裂现象,表明马氏体也参与了较大程度的变形。 相似文献
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研究了2个级别双相钢HC590DP和HC780DP在小应变下的单轴拉伸性能和纯弯曲性能。结果表明:在产生塑性应变初始阶段,相同应变下HC780DP应力反而小于HC590DP,但通过某临界点后,HC780DP应力超过HC590DP。2种材料在0.02%的小应变时,弯曲强度均大于拉伸强度;且材料在弯曲过程中的应变强化硬化能力要高于单轴拉伸;相比冲压成形,HC590DP和HC780DP在弯曲变形加工过程中(如辊压、折弯成形)的材料变形抗力大,塑性加工硬化率高,回弹量大。 相似文献
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利用OM, SEM, TEM及XRD等,对不同退火温度下热轧Fe-12Mn-8Al-0.8C轻质钢的组织演变及力学性能进行了研究.研究结果表明,较低温度下退火时,实验钢组织为奥氏体+铁素体+κ-碳化物.随着退火温度的升高,实验钢中κ-碳化物发生溶解,奥氏体晶粒尺寸逐渐增加,实验钢的屈服强度和抗拉强度逐渐降低,伸长率则先增大后降低.不同退火温度下实验钢应变硬化行为的差异与其组织组成有关.750℃退火0.5 h的实验钢具有铁素体+κ-碳化物体积分数较高的复相组织,其加工硬化能力较高.随着退火温度的升高,铁素体与κ-碳化物的体积分数逐渐降低,应变硬化率有所降低,但应变硬化行为表现得更为持续.950℃退火0.5 h的实验钢与其他退火温度下的实验钢相比,获得了良好的综合性能,抗拉强度为930 MPa,伸长率为35.48%,韧脆转变温度约为-40℃. 相似文献
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The microstructure and mechanical properties of cold rolled TRIP steel containing C 0.2, Si 0.5, Mn 1.5, A1 1.3, and Nb-kV 0.13 (mass%) with annealed martensite (TAM steel) were investigated using optical microscopy, field emission gun scanning electronic microscope (FEG SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and mechanical testing. The mierostructure of the TAM steel mainly consisted of polygonal ferrite, bainite, annealed martensite and retained austenite. The martensite after annealing did not spheroidize, which consisted of annealed lath martensite structure and interlath second phase. Compared with the traditional TRIP steel with polygonal ferrite matrix (TPF steel), the TAM steel has more excellent elongation rate over 32%. The TAM steel also has better strain hardening behavior than the TPF steel. The excellent elongation and strain harden- ing behavior of TAM steel result from high retained austenite stability of the TAM steel, which is attributed to its fine distribution and medium strength ratio of second phase to matrix. 相似文献
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The microstructures and mechanical properties of ferrite-based lightweight steel with different compositions were investigated by tensile test,scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD)and thermodynamic calculation(TC).It was shown that the ferrite-based lightweight steels with 5wt.%or 8wt.%Al were basically composed of ferrite,austenite andκ-carbide.As the annealing temperature increased,the content of the austenite in the steel gradually increased,while theκ-carbide gradually decomposed and finally disappeared.The mechanical properties of the steel with 5wt.%Al and 2wt.%Cr,composed of ferrite and Cr7C3carbide at different annealing temperatures,were significantly inferior to those of others.The steel containing 5wt.%Al,annealed at 820°C for 50sthen rapidly cooled to 400°C and held for 180s,can obtain the best product of strength and elongation(PSE)of 31242MPa·%.The austenite stability of the steel is better,and its PSE is higher.In addition,the steel with higher PSE has a more stable instantaneous strain hardening exponent(n value),which is mainly caused by the effect of transformation induced plasticity(TRIP).When theκ-carbide or Cr7C3carbide existed in the microstructure of the steel,there was an obvious yield plateau in the tensile curve,while its PSE decreased significantly. 相似文献
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为了研究临界退火中锰钢的微观组织演变规律以及组织对力学性能和变形行为的影响,对冷轧中锰钢(0.1C-7Mn-0.35Si)在570~650 ℃范围内进行了临界退火处理。研究结果表明,随着退火温度升高,双相“奥氏体+铁素体”组织逐步趋于等轴化且晶粒有粗化的趋势,并且在650 ℃时出现了马氏体组织;试验钢的抗拉强度随温度升高而增加,而伸长率和屈服强度均呈下降趋势,局部不均匀变形带随着退火温度升高逐步弱化,在620和650 ℃时完全消失;在相对较高的退火温度下,粗化的等轴奥氏体晶粒中形变诱导马氏体相变的增强和大尺寸的铁素体晶粒中动态回复的减弱,以及更高温度时马氏体的引入等,均改善了屈服阶段的加工硬化能力,从而有效减弱或抑制吕德斯带的扩展。 相似文献
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I. Hajiannia M. Shamanian M. Atapour E. Ghassemali N. Saeidi 《Transactions of the Indian Institute of Metals》2018,71(6):1363-1370
A new transformation induced plasticity (TRIP) steel containing high volume fraction of martensite was produced by austempering heat treatment cycle. Microstructure and tensile properties of this TRIP steel were investigated and compared to those of a dual phase (DP) steel with high martensite volume fraction. Microstructural analysis showed a mixture of ferrite, bainite, retained austenite and about 25–30 vol% of martensite in the TRIP steel. As a result of the strain induced transformation of retained austenite to martensite, the TRIP steel showed a strength elongation balance of 86% higher than that for the DP steel. In comparison to the commercial TRIP780 steel, the current TRIP steel showed a 15% higher ultimate tensile strength value while maintaining the same level of ductility. TRIP steel also had a larger work hardening exponent than DP steel at all strains. 相似文献
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为研究980 MPa级C-Si-Mn-Nb系冷轧双相钢组织性能,在试验室冶炼该钢并采用临界区保温+两段式冷却+过时效处理的工艺进行热处理。研究表明,试验钢的屈服强度为476 MPa,抗拉强度为1 021 MPa,伸长率为15%,n值为0.29;试验钢热轧组织为(F+P),铁素体晶粒尺寸约为3.3μm;退火组织为(F+M),马氏体体积分数约为63%。微合金元素Nb的添加,起到细晶强化和析出强化的作用。与热轧组织相比,连续退火板带状组织得到明显改善,试验钢表现出良好的强韧性匹配。 相似文献
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The influence of hot-rolled process on microstructure in TRIP steel and the heredity characteristic from the hot-rolled microstructure to annealed microstructure are investigated. The results show there are two kind of hot-rolled microstructures under different coiling temperatures. One is composed of coarse grains of ferrite, pearlite and bainite, and the other is composed of small grains of ferrite, bainite and austenite. After annealing, the first kind of hot-rolled microstructure is greatly refined, and volume fraction, carbon content of austenite increase significantly. However, it have little changes in grain size, volume fraction and carbon content of austenite after the second kind of hot-rolled sheet is annealed. There are also differences in distribution of retained austenite between the two annealed microstructures observed by EBSD and TEM technology. Retained austenite in the first annealed microstructure distributes mainly inside of the polygonal ferrite in the form of spot, only little retained austenite on bainte ferrite boundary, however retained austenite in the second annealing microstructure allocates several places, such as inside of polygonal ferrite, on polygonal ferrite boundary, on bainte ferrite boundary. 相似文献
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摘要:对中碳钢采用Q&P(淬火 碳分配)和I&QP(临界热处理,淬火 碳分配)热处理工艺,通过对试样的显微组织,残余奥氏体的体积分数及其碳含量,硬度及其拉伸性能进行分析,研究了临界加热对中碳Q&P钢组织和性能的影响。实验结果表明,经临界热处理的Q&P钢组织中,除了马氏体和残余奥氏体,还存在部分铁素体,同时残余奥氏体的体积分数较少,马氏体板条更加细小。在相同的碳分配时间下,I&QP试样的硬度和抗拉强度都比Q&P试样低,但由于I&QP试样中软相铁素体的存在以及残余奥氏体能发挥更好的TRIP效应,使得临界热处理的实验钢的伸长率更高,加工硬化指数增加,强塑积更大。 相似文献