两相区退火处理含铝中锰钢的组织和力学性能

 为了研究两相区退火处理对冷轧含铝中锰钢(0.2C-0.6Si-5Mn-1.2Al)(质量分数,%)微观组织和力学性能的影响规律,利用SEM、XRD及单轴拉伸等试验方法表征了不同工艺状态后的微观组织及测试了拉伸性能。结果表明,冷轧试验钢在退火过程中组织发生奥氏体逆转变,在退火温度为670 ℃、退火时间为10 min时可获得较佳的力学性能,即抗拉强度达到1 276 MPa,总伸长率达到51.8%,强塑积高达66.1 GPa·%。随着退火温度升高,残余奥氏体组织逐渐粗化且向马氏体组织转变,机械稳定性逐渐降低。残余奥氏体机械稳定性主要受残余奥氏体中碳质量分数及其晶粒尺寸的影响,而残余奥氏体中锰质量分数对其影响较小。     

基于退火路径的中锰钢组织转变与力学性能

为了更好地指导中锰钢工业试制,利用扫描电镜、电子背散射衍射、透射电镜和拉伸试验机等研究了不同退火路径下低碳中锰钢的组织转变及合金元素配分行为,并评价了其对力学性能的影响.结果表明,热轧中锰钢的显微组织主要由铁素体、板条马氏体、粒状贝氏体和残余奥氏体构成.经冷轧变形后,原组织中的铁素体和马氏体晶粒破碎,残余奥氏体和M/A...     

一种Fe-C-Si-Mn-Cr-Mo钢碳配分行为对组织的影响

 利用Formastor-FⅡ全自动相变仪模拟研究了一种Fe-0.24C-0.3Si-1.0Mn-0.56Cr-0.17Mo（质量分数,%）钢在冷却过程中的碳配分行为及其对马氏体和残余奥氏体的影响,用扫描电镜、透射电镜进行微观组织表征,用X射线衍射法和电子背散射衍射法测定残余奥氏体体积分数。结果表明,试验钢分别经末段慢冷和直接快冷工艺冷却后均获得马氏体＋残余奥氏体两相组织,其中直接快冷工艺所得马氏体相对杂乱,尺寸较小,残余奥氏体体积分数较少;而末段慢冷工艺所得马氏体板条较长,且发生了碳的配分,残余奥氏体体积分数较多,以薄膜状分布在马氏体板条间,板条内部含有高密度位错。     

深冷对逆相变处理中锰钢组织性能的影响

摘要：为了研究原始组织状态对逆相变退火中锰钢微观组织和力学性能的影响,对淬火处理的中锰钢再进行-74℃深冷处理,采用SEM、EBSD、XRD等手段评价了逆相变退火处理后的微观组织,用单轴拉伸和冲击试验评价力学性能。研究结果表明：淬火态中锰钢的组织由马氏体和体积分数约为33%的残余奥氏体组成,深冷处理后得到残余奥氏体体积分数小于15%的细小马氏体组织;相对于淬火+逆相变处理的样品,深冷+逆相变样品奥氏体体积分数从31%提高到49%,具有更高的奥氏体稳定性使屈服强度从650MPa提高到852MPa,断后伸长率从22%提高到37%。     

深冷对逆相变处理中锰钢组织性能的影响

为了研究原始组织状态对逆相变退火中锰钢微观组织和力学性能的影响,对淬火处理的中锰钢再进行-74℃深冷处理,采用SEM、EBSD、XRD等手段评价了逆相变退火处理后的微观组织,用单轴拉伸和冲击试验评价力学性能。研究结果表明:淬火态中锰钢的组织由马氏体和体积分数约为33%的残余奥氏体组成,深冷处理后得到残余奥氏体体积分数小于15%的细小马氏体组织;相对于淬火+逆相变处理的样品,深冷+逆相变样品奥氏体体积分数从31%提高到49%,具有更高的奥氏体稳定性使屈服强度从650 MPa提高到852 MPa,断后伸长率从22%提高到37%。     

含钛中锰钢淬火-配分组织及力学性能

 为了研究淬火-配分含钛中锰钢的组织与力学性能,借助扫描电子显微镜,透射电子显微镜、电子背散射衍射技术与万能拉伸试验机、磨粒磨损试验机等,分析与测试了含钛中锰钢在165~240 ℃淬火380 ℃配分处理后组织、强度、塑性与磨粒磨损性能。结果表明,试验钢淬火-配分组织主要为板条状一次马氏体、块状二次马氏体及残余奥氏体,同时含有大量微米级TiN和纳米级(Ti,Mo)C及TiN-(Ti,Mo)C复合析出相。190 ℃淬火380 ℃配分后残余奥氏体体积分数最高为12.5%。试验钢不同温度淬火与配分后屈服强度均大于1 000 MPa,抗拉强度均大于1 500 MPa,硬度从482.5HV增大到542.2HV,伸长率范围为9.2%~14.5%,在165~190 ℃淬火-配分处理后其抗磨粒磨损性能优于220~240 ℃淬火-配分钢。磨损机制主要是塑性变形和疲劳破坏,磨损过程中残余奥氏体发生应变诱导马氏体相变(TRIP)效应,析出相颗粒阻断基体塑性变形过程犁沟的前进和刮削行为,含钛中锰钢通过淬火-配分引入一定体积分数的残余奥氏体,有利于提高钢的强塑性与抗磨损性能。结合力学性能指标,含钛中锰钢最佳淬火-配分工艺为900 ℃奥氏体化30 min,190 ℃淬火,380 ℃配分10 min。     

中锰钢逆相变退火组织的演变及锰的配分行为

采用 SEM、TEM、STEM、XRD、EBSD 等实验分析方法对中锰钢(0.2C5Mn)在奥氏体逆相变不同时间退火过程中的微观组织演变进行了分析.结果表明：中锰钢在650℃短时间逆相变退火时析出大量 M3 C 型碳化物,随着退火时间的延长,逆相变奥氏体形成长大,获得马氏体、奥氏体双相片层状组织.马氏体与逆相变奥氏体晶粒取向服从 K-S 关系,且两相板条平均宽度在0.5μm 左右.退火过程中锰元素出现由淬火组织平均分布逐渐向逆相变奥氏体富集的配分行为,长时间退火后形成体积分数为30％的逆相变奥氏体,抗拉强度为960 MPa,屈服强度为500 MPa,总伸长率为40％,强塑积高达38.4 GPa??％.     

热处理工艺对膨胀管组织和力学性能的影响

采用两相区热处理工艺研究了膨胀管用低碳中锰钢组织演变规律和力学性能。结果表明:采用两相区热处理工艺的低碳中锰钢组织为回火索氏体+富碳马氏体/贝氏体+少量铁素体的复相组织+残余奥氏体,残余奥氏体分布在原奥氏体晶界上和马氏体/贝氏体板条界上,残余奥氏体主要通过临界淬火富集C和Mn元素达到稳定,室温下稳定的残余奥氏体含量最高可达12%。由于残余奥氏体的应变诱导塑性(TRIP)效应,低碳中锰钢具有良好的塑性,断后总延伸率高于40%,均匀延伸率高于20%。     

常化后冷却工艺对1600MPa级超高强钢组织性能的影响

为改善高强度钢的塑性和韧性,对中碳低合金马氏体高强度钢分别采用常化后空冷＋回火和常化后控冷＋回火工艺,研究常化后冷却工艺对钢中残余奥氏体及力学性能的影响.采用扫描电镜获得钢的组织形态,利用X射线衍射和电子背散射衍射技术分析钢中残余奥氏体的体积分数、形貌和分布.发现两种工艺下均得到板条马氏体＋残余奥氏体组织,残余奥氏体均匀分布在板条之间,随工艺参数不同,其体积分数在3%~10%变化.常化后加速冷却能显著细化马氏体板条,提高钢的屈服强度和抗拉强度100 MPa以上,冲击功下降4 J.残余奥氏体的体积分数随常化控冷终冷温度的升高呈现先升高后降低的变化,常化后的控制冷却也可以作为进一步改善马氏体类型钢组织和性能的方法      

超细晶中锰钢温轧强化增塑机理

采用Gleeble-3500热模拟试验机测定了不同温度下中锰钢的变形抗力,并通过分阶段拉伸、扫描电镜、电子背散射衍射、X射线衍射等实验手段,对温轧中锰钢中逆转变奥氏体的相变行为进行观察和分析。研究发现,热轧马氏体中锰钢经过600℃温轧及退火后,获得较多较稳定的残余奥氏体,从而实现强度859 MPa和延伸率36%的优良力学性能。拉伸变形前期,锯齿状流变应力现象明显,残余奥氏体提供持续的TRIP效应来提高塑性,此过程中尺寸较大的逆转变奥氏体稳定性差,变形时先发生转变;拉伸变形后期,锯齿状波动消失,超细晶铁素体和马氏体发生塑性变形,马氏体强化及铁素体中的位错强化为主要强化方式。      

Retained austenite and mechanical properties of 0. 1C- 5Mn steel after intercritical annealing

The effect of annealing temperature on the microstructure, mechanical property and austenite content for 0. 1C- 5Mn steel was studied by ART (Austenite Reverted Transformation) heat treatment process. The morphology, metastable austenite content and mechanical properties of experimental steel were characterized by means of SEM, XRD and tensile testing at room temperature. The results indicate that the structure of experimental steel is composed of ferrite and retained austenite; with the increase of the inintercritical annealing temperature, precipitation and redissolution of carbides are found in experimental steels; simultaneously, the lath- like deformed martensite reverts to form equiaxed ferrite through the recovery and polygonization, and granular austenite undercools to lath- like and blocky martensite; the contents of retained austenite are similar in 630, 645 and 660?? samples, which are 18. 4 vol.%, 19. 5 vol.% and 18. 8 vol.%, respectively; with the increase of the annealing temperature, the volume fraction of the retained austenite suddenly drops and a large amount of reversed austenite changes into martensite; the combination of different annealing temperatures indicates that the experimental steel can obtain the best comprehensive mechanical properties when the annealing temperature is 660??.     

Microstructure and Mechanical Properties of High Manganese TRIP Steel

 Abstract： Microstructure evolution and mechanical properties of newly designed 01C-6Mn-05Si-1Al TRIP-aided steels under different annealing conditions and the effects of matrix microstructure before intercritical annealing on the final microstructure were studied by means of X-ray diffraction (XRD), scanning electron microcopy (SEM), dilatometric simulation, optical microstructure (OM) and tensile testing in this work. The experimental results indicate that the TRIP steel with Mn of 6% could form a considerable amount of retained austenite with good TRIP effect after a simple intercritical annealing treatment, and the matrix microstructure before intercritical annealing treatment can greatly affect the final microstructure. The original microstructure of the ferritic matrix steel was eliminated, while annealed martensite was remained from the martensite matrix steel under the same intercritical annealing conditions.     

The improvement of cryogenic mechanical properties of Fe-12 Mn and Fe-8 Mn alloy steels through thermal/mechanical treatments

An investigation has been made to improve the low temperature mechanical properties of Fe-8Mn and Fe-12Mn-0.2 Ti alloy steels. A reversion annealing heat treatment in the two-phase (α+ γ) region following cold working has been identified as an effective treatment. In an Fe-12Mn-0.2Ti alloy a promising combination of low temperature (-196°C) fracture toughness and yield strength was obtained by this method. The improvement of properties was attributed to the refinement of grain size and to the introduction of a uniform distribution of retained austenite (γ). It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated α martensitic structure and absence of ε martensite. As a result, a significant reduction of ductile to brittle transition temperature was obtained. formerly with the Lawrence Berkeley Laboratory, University of California.     

不同热处理工艺对Nb-Mo中锰钢组织和力学性能的影响

摘要：探讨了不同热处理工艺对Fe-0.25C-3.98Mn-1.22Al-0.20Si-0.19Mo-0.03Nb中锰钢组织演变与力学性能的影响。研究发现,与临界退火和淬火配分（IA & QP）工艺相比,奥氏体逆转变（ART）工艺处理后的实验钢获得了更为优异的力学性能;采用ART工艺经过680℃临界退火5h后的实验钢展现出了最佳的力学性能,即抗拉强度为830MPa,伸长率为48.9%,强度与塑性的乘积达到40.6GPa·%;ART工艺实验钢因长时间退火而促进了Mn向奥氏体中富集,有利于奥氏体含量及稳定性增加,在应变中后期可展现更为广泛的TRIP效应,更有利于获得优异的力学性能。另外,微合金元素Nb和Mo在中锰钢主要起析出强化和细晶强化的作用。     

Role of retained austenite on the deformation of an Fe-0.07 C-1.8 Mn-1.4 Si dual-phase steel

The influence of retained austenite on the work hardening behavior of dual-phase steel has been investigated with an Fe-0.07 C-1.8 Mn-1.4 Si steel. With a constant cooling rate of 5 °C per second after intercritical annealing at 780 °C, a significant quantity (about 8 vol pct) of retained austenite was obtained in the dual-phase microstructure. The retained austenite was classified morphologically into either ‘isolated’ or ‘capsulated’ types by TEM observation. The ‘capsulated’ type, which was found without a particular shape inside the microtwinned martensite particle, withstood much deformation by being protected by the surrounding martensite. While the ‘isolated’ type, which was found with an equiaxed shape and was isolated from martensite particles, was easily deformed by the first several percent plastic strain. The increase in work hardening rate, caused by the strain induced transformation of retained austenite to martensite, was ascribed to the contribution of the ‘isolated’ type, the major volume fraction of retained austenite. The effect of the retained austenite on the yielding of dual-phase steel was not indicated since the reduction in the volume fraction of retained austenite was negligible at the initial deformation stage.     

碳含量对Fe-Mn-Cu-C系TWIP钢组织和力学性能的影响

 采用真空熔炼法制备Fe-20Mn-3.0Cu-XC系高强度高塑性合金钢,通过X射线衍射（XRD）、光学显微镜（OM）和透射电子显微镜（TEM）观察方法研究了碳含量对该系列合金微观组织和力学性能的影响,分析了合金的拉伸变形微观机制。结果表明：Fe-20Mn-3.0Cu-XC系合金拉伸变形前后均为单相奥氏体组织,未发生马氏体相变。随着碳质量分数的增加,合金的屈服强度、抗拉强度和伸长率均显著提高。Fe-20Mn-3.0Cu-1.41C合金的屈服强度为501.62MPa,抗拉强度为1178.4MPa,具有优异的综合力学性能。Fe-20Mn-3.0Cu-XC系合金具有优异的应变硬化能力。随着碳质量分数增大至1.41%,最大应变硬化指数n值达到0.782。Fe-20Mn-3.0Cu-XC系合金拉伸变形过程中,TWIP效应是主要的塑性变形机制,大量位错的塞积、形变孪晶的形成以及位错与孪晶间的交互作用共同引起材料强度和塑性的提高。     

Annealing Temperature Dependence of the Tensile Behavior of 10 pct Mn Multi-phase TWIP-TRIP Steel

In the present study, the relationship between the microstructure and the mechanical properties of Fe-10 pct Mn-3 pct Al-2 pct Si-0.3 pct C multi-phase steel was investigated. The 10 pct Mn multi-phase steel exhibits a combination of high tensile strength and enhanced ductility resulting from deformation-twinning and strain-induced transformation occurring in succession. A pronounced intercritical annealing temperature dependence of the tensile behavior was observed. The annealing temperature dependence of the retained austenite volume fraction, composition, and the grain size was analyzed experimentally, and the effect of the microstructural parameters on the kinetics of mechanical twinning and strain-induced martensite formation was quantified. A dislocation density-based constitutive model was developed to predict the mechanical properties of 10 pct Mn multi-phase steel. The model also allows for the determination of the critical strain for dynamic strain aging effect.