铌硼微合金钢高温应变诱导析出行为

用应力弛豫方法研究了超低碳铌硼微合金钢在８００℃，８５０℃、９００℃和９５０℃下，经过２０％预变形目的等温应变诱导析出行为。样品的透射电镜观察表明：应变诱导析出只在位错线上形核并阻碍位错运动，而位错一旦摆脱钉扎，这种运动位错可以是样品中进一步析出的优先形核位置，从而导致析出分阶段进行。     

含Nb微合金钢应变诱导析出的研究现状

简述了微合金钢中微量元素Nb的主要作用,回顾了应变诱导析出的研究方法及优缺点,阐明了变形奥氏体应变诱导析出相的种类,晶体结构,析出相的形成顺序、形貌和分布,分析了影响析出动力学的主要因素并简要介绍了应变诱导析出动力学模型的最新发展.     

IF钢中的析出物

概述了不同IF钢中析出物的种类、特征和析出规律,介绍了不同元素对析出物种类和析出过程的影响,轧制和退火过程中析出物演变的研究现状,指出了析出物今后的重点研究方向.     

热轧双相钢的发展现状及高强热轧双相钢的开发

介绍了热轧双相钢的发展现状及存在问题,指出低成本热轧双相钢、高延伸凸缘型铁素体+贝氏体热轧双相钢(F-B热轧双相钢)及高强度热轧双相钢的开发及应用,将促进我国热轧双相钢的发展,推动汽车工业的"以热代冷"进程。同时,探讨了纳米析出强化型热轧双相钢的强化机理及工艺控制原理,并在实验室进行了中试,开发出铁素体基体析出强化型的热轧双相钢,其抗拉强度达770~830 MPa,屈强比0.75,组织为铁素体+马氏体,且铁素体基体中存在大量细小的纳米级尺寸的TiC过饱和析出和相间析出。     

低活化钢析出相热力学研究

设计了一种低碳低活化铁素体/马氏体钢,利用扫描电镜、透射电镜和拉伸实验等方法观察和测定了实验钢在不同制备工艺下的显微组织和力学性能,并对其析出物进行EDS化学成分检测,同时通过热力学计算研究了低碳低活化钢析出相的析出规律。结果表明:热轧后经980℃保温1h完全奥氏体化淬火与750℃保温1h空冷处理后,能够制备出性能达标的超低碳实验钢;析出相主要为M_(23)C_6和MX相,其中M_(23)C_6主要在950℃以下轧制和热处理过程中析出,而MX主要在轧制过程中大量析出,同时在快速冷却和热处理过程中的二次析出比较少。     

热轧双相钢的低温拉伸

研究了 Si-Mn-Cr-Mo 系列热轧双相钢从室温到-180℃,三种不同应变速率下的低温性能和断裂特征。结果发现此钢具有良好的低温延性。在三种应变速率下,随实验温度的降低,在断裂强度和屈服强度增加的同时延伸率基本保持不变。在相同试验温度下,断裂强度与应变速率无关,而高应变速率使屈服强度有所增加,使延伸率稍有降低。用 SEM 和 TEM 对各种样品断口和位错组态观察表明:此钢的冷脆转变温度在-100—-140℃之间,并且随实验温度的降低,马氏体的位错组态发生了相应的变化。微观结构的变化反映了材料的加工硬化能力,并且与宏观力学性能的变化相对应。     

低密度钢中有序析出相的研究进展

随着"减重、节能、降低碳排放"的绿色制造理念越来越深入人心,对传统钢铁材料升级换代的需求显得尤为迫切,第三代汽车用钢已成为各国研发机构和企业关注的焦点。高强度、高韧性、轻量化的先进钢铁材料成为第三代汽车用钢的一个新的研发方向。主要通过在Fe中添加较多的轻质元素如Al、Mn、Si等进行合金成分设计来显著降低钢材密度;同时通过调控基体组织和析出相构成、形态来平衡钢材的强度和塑韧性,从而使钢具有高的强塑积和低的密度。本文针对Fe-Al、Fe-Mn-Al、Fe-Mn-Al-C系低密度钢的成分及组织特征,介绍了低密度钢中Kappa碳化物,(Fe,Mn) Al、Ni Al型B2相,(Fe,Mn)_3Al型DO_3相和β-Mn相的晶格参数及相关性能特征。结合国内外对低密度钢的最新研究,着重对低密度钢相图的热/动力学计算、各有序析出相的元素配分和析出行为(特征、形态、大小)、析出相对钢组织演变与强韧性机制的影响等进行了总结,并基于现有的研究,展望了高强度、高韧性、低密度钢进一步的研究方向。     

热处理对21-2N钢层状析出的影响

研究了不同热处理制度对21-2N钢层状析出的影响,试验表明,不同固溶温度处理,21 2N钢的层状析出量不同.不同固溶温度处理后,在750℃长时时效后的层状析出量、析出大小、形态、分布也不同.     

ODS钢中纳米氧化物析出长大机制的研究进展

纳米氧化物弥散强化(Oxide dispersion strengthened, ODS)钢得益于基体中弥散分布的超高数量密度的纳米氧化物粒子，具有优异的综合服役性能，被视为第四代裂变堆包壳以及未来聚变堆包层的优选结构材料。传统制备ODS钢最主要的方法是机械合金化(Mechanical alloying, MA)等先进粉末冶金技术，且对其制备样品中氧化物粒子性质的研究较为深入。由于机械合金化在工程应用上有一定局限性，近年来提出以液态金属(Liquid metal, LM)路线制备ODS钢。目前液态金属路线中的真空熔炼法是最常用也是相对比较成功的方法，但与机械合金化相比仍有一定的差距。本文主要总结了机械合金化制备的ODS钢中纳米氧化物的析出机制、长大行为以及其他元素的添加对其产生的影响等，同时对液态金属路线的工艺进程及真空熔炼法的研究现状进行概述，并对机械合金化未来所需解决的问题和液态金属路线的后续发展、工艺优化等进行了展望，为液态金属路线的后续研究工作提供参考。     

Simulated Calculations of Strain Induced Precipitation Behaviorin a Nb-Ti-V Steel

On the basis of regular solution sublattice model and classical nucleation and growth theory Strain induced precipitation kinetics in Nb-Ti-V combined treated microalloying Steels has been calcu lated. The calculated precipitation-time-temperature (PTT) diagram is in reasonable agreement with experimental results obtained from isothermal Stress relaxation method.     

一种CrMnN不锈钢中碳化物等温沉淀动力学的研究

用膨胀仪、化学定量相分析（ＣＰＡ）及ＴＥＭ方法研究了ＺＧ０Ｃｒ１３Ｍｎ８Ｎ钢奥氏体中碳化物的等温沉淀动力学。结果表明，依据等温不同时间析出碳化物引起的Ｍｓ温度变化可更方便，更准确地测出奥氏体中碳化物等温沉淀动力学曲线；在９００￣５８０℃范围内ＺＧ０Ｃｒ１３Ｍｎ８Ｎ钢中碳化物等温析出的鼻尖温度为８００℃，相应的孕育期为２４００Ｓ；碳化物主要以Ｍ２３Ｃ６型沿晶界或夹杂物边界析出。     

Bond Graph Modelling and Simulation of Static Recrystallization Kinetics in Multipass Hot Steel Rolling

In hot rolling, the final thickness of the strip is achieved through plastic deformation of the original stock by a series of counter-rotating rollers. In this work, static recrystallization kinetics in between two stages of steel rolling has been modelled, and simulation studies have also been performed to find out the effect of entry temperature on the recrystallization kinetics. A viable bond graph model has been developed to study the kinetics of the process. Low-carbon steel has been considered for this purpose.     

电工钢中柱状晶热压缩时取向的变化及对析出的影响

利用电子背散射衍射(EBSD)技术和场发射电子扫描显微镜(FESEM)研究了电工钢中柱状晶不同初始取向50%热压缩变形后的演变规律及其对粒子析出行为的影响。结果表明:〈100〉晶粒形变后仍为〈100〉取向,只发生绕ND∥〈100〉方向的转动,具有遗传性,粒子析出数量少。柱状晶长轴与压缩轴的偏转度增加,取向的稳定性变差,超过40°,可形成〈111〉取向,期间发生复杂的滑移系交互作用,产生较高的缺陷密度,促进粒子析出。MnS粒子主要在晶内析出,变形温度高、形变量低,粒子均无法充分析出。回复时,形变晶粒内高的储能和缺陷密度是促进粒子进一步析出的必要条件。     

高速钢高温形变诱发析出的研究

本文探讨了高速钢在高温形变过程中碳化物析出的行为及奥氏体组织状态对析出的影响。用透射电镜和扫描电镜分析了不同热处理状态奥氏体的组织结构,分析了高温形变过程中碳化物析出的部位,颗粒尺寸及形态。试验表明, 碳化物主要在奥氏体的缺陷处呈点状和点列状析出,大小为20mμ。处于回复状态的奥氏体缺陷诱发碳化物析出,析出碳化物钉札缺陷阻止再结晶进行。当再结晶驱动力较大时,由于动态再结晶充分发展,使缺陷大量消除,碳化物析出显著地减少。     

Dynamic Recrystallization and Precipitation Behavior of Mn-Cu-V Weathering Steel

The hot deformation behavior of a Mn-Cu-V weathering steel was investigated at temperatures ranging from 850 to 1050℃ and strain rates ranging from 0.01 to 5 s-1 using MMS-300 thermal-mechanical simulator. The activation energy for dynamic recrystallization and stress exponent were calculated to be 551 kJ/mol and 7.73, respectively. The accurate values of critical strain were determined by the relationship between work hardening rate and flow stress (θ-σ) curves. The hyperbolic sine constitutive equation was employed to describe the relationship between the peak stress and Zener-Hollomon parameter during hot deformation. The interaction between dynamic recrystallization and dynamic precipitation of V(C,N) at a low strain rate was analyzed. The results showed that precipitation particles size of weathering steel increased with increasing strain at deformation temperature 950℃ and strain rate 0.1 s-1. The calculation results of the recrystallization driving force and pinning force showed that dynamic precipitation could retard the progress of dynamic recrystallization but not prevent it while the pinning forces is less than driving force. On the contrary, dynamic precipitation can effectively prevent the progress of dynamic recrystallization.     

Split Ends and Cracking Problem During Hot Rolling of Continuously Cast Steel Billets

The paper presents a detailed analysis of split end and cracking problems that occurred during hot rolling of thermomechanically treated (TMT) grade steel bars. The major analytical tool was a multiscan computer-controlled ultrasonic image analysis system for analysis of the defects observed on transverse cut slices of the billets under investigation. The possible reasons for billet cracking during hot rolling such as a low Mn/S ratio, high casting speed, high degree of superheat, and high inclusion content in steel were analyzed. Additionally in the process parameters such as low roll diameter, high friction, and low reduction ratio were also analyzed. The cracking appeared to be associated with large surface/internal defects, axial porosity, off-centered cavities/porosities, off-centered cracks, and inclusion bands. The analysis results suggested methods to prevent such defects in continuously cast steel billets and to reduce/eliminate split end problems. The casting parameters should include: (a) Mn/S ratio >35, (b) degree of superheat <60 °C, and (c) casting speed: <3.0 m/min, where roll radius and initial thickness of the workpiece should be optimized.     

40CrNiMoA钢超塑流变初期形变诱发连续再结晶过程的研究

用 TEM 研究了40CrNiMoA 钢超塑变形初期的动态回复、动态再结晶过程,结果发现:随应变量的增加,多边化形成的小角度亚晶界不断吸收晶格位错而逐渐转变为大角度晶界,为晶界滑动提供了条件.     

Influence of RPC Parameters on the Precipitation of Nb in Microalloyed Steel

Thermo-simulation test, metallographic analysis, measurement of hardness, TEM(including diffraction contrast technique and nano-beam anylasis)along with calculating software of Metlab, etc. were used to study the influence of RPC parameters(relaxation time, aging time)on the precipitation of Nb in microalloyed steel. Following work was undertaken in this study:Strain-induced precipitation in Nb-bearing multi-microalloyed steel was monitered and analyzed. The interaction between dislocation evolution and precipitates in deformed austenite was directly observed(an Fe-Ni-Nb alloy was employed to simulate austenite in steel). The(a low carbon microalloyed steel only by Nb was adopted)effect of relaxation of deformed austenite on aging behavior occurring in bainite was investigated. Finally, the thermal stability and variation of composition of carbonitride precipitates during dissolving process in Nb-Ti microalloyed steel were alsodetected. These results indicate:(1)During the stress relaxation, the process of precipitation happened in deformed austenite of multi-microalloyed steel can be divided into three stages, i. e. nucleation, growth and coarsening. In the final stage of relaxation, Mo atoms would enter the lattice of(Nb,Ti)(C,N)precipitates and its concentration in the precipitates increases with the relaxation time.(2)In the earlier stage of relaxation, the dislocations in deformed austenite demonstrate twisted and distribute randomly. The precipitates have the tendency to occur along those dispersed dislocations. The dilocation cells would form gradually with the relaxing time prolonged and would become more stable by the subsequent precipitates formed on them in the later relaxation period. The paralleled dislocations in dislocation cells exhibit the same Burgers vector. The dislocations get rid of pinning by the bypassing mechanism.(3)When the samples are reheated to hold isothermally at 525℃,which are relaxed for different time in deformed austenite followed by accelerated cooling, their microstructures evolve very slowly with the aging time but two hardness peaks can be found one each hardness-time curves. The position of hardness peaks nearly raimains unchanged while their height varies obviously with the relaxation time. In no relaxtion samples, only one hardness peak could be observed. During the process of aging at 525℃, The growth and coarsening of as-existed strain-induced precipitates formed in deformed austenite contribute to formation of the first hardness peaks. While the second hardness peaks result from the further precipitates which nucleate in a phase after γ→α transformation(after aging for about 10 hours).(4)It was found that the precipitates formed during solidification are monophase(Ti,Nb)(C.N)rather than TiN enclosed with NbC. With addition of Ti to the steel, the thermal stability of the carbonitrides would enhance remarkably.