23MnNiCrMo钢的相变及组织特征

对 2 3MnNiCrMo煤机链条钢进行了连冷转变、等温转变、回火转变的研究 应用日本Formastor -Digital全自动相变膨胀仪测定了临界点 ,研究了过冷奥氏体的等温分解过程 ,应用电子显微镜分析了各类转变产物的组织结构 结果表明 ,2 3MnNiCrMo贝氏体钢具有一系列的相变特征和组织特点     

Characteristics of microstructural evolution during deformation-enhanced ferrite transformation in Nb-microalloyed HSLA steel

Microstructure evolution during deformation of undercooled austenite at 760℃ was investigated in Nb-microalloyed steel by using SEM （scanning electron microscope）, TEM （transmission electron microscope）, and EBSD （electron backscattered diffraction）. It is indicated that during deformation-enhanced ferrite transformation （DEFT） in Nb-microalloyed steel, the incubation period is prolonged, and the higher strain is needed to accomplish ferrite transformation. Therefore, the transformation kinetics curves move to high strain parallelly; and the transformation kinetics curves of Nb-microalloyed steel can be divided into three stages. At the fast stage, the solute drag effect of Nb and the consumption of strain energy for the dynamic precipitation of Nb（CN） led to a long incubation period, and at the second stage, ferrite transformation was accelerated significantly and fine Nb（CN） precipitates restrict the grain growth of ferrite effectively. The results also showed that DEFT in Nb-microalloyed steel is still a nucleation dominated process, and during the microstructure evolution the interchange of 〈001〉 and 〈111〉 texture was obtained.     

含铌微合金钢冷却过程热模拟研究

在Gleeble1500D热模拟机上,利用热膨胀法测定了含铌微合金钢连续冷却转变曲线(CCT曲线),分析了成分对冷却转变的影响,为进一步制定生产工艺提供了依据.     

Effect of Nb on the transformation kinetics of low carbon （manganese） steel during deformation of undercooled austenite

The hot compression tests using Gleeble 1500 were performed by varying the true strain up to 1.6 （80% reduction） in Nbfree and Nb-microalloyed steels. The effect of Nb addition on the transformation kinetics during deformation of undercooled austenite was investigated. It was found that as compared with Nb-free steel, the transformation incubation period of Nb-bearing steel was prolonged and the transformation kinetics curves parallelly moved to higher strain because of the solute Nb drag effect. Studies on kinetics also showed that the deformation-enhanced ferrite transformation （DEFT） of the two steels were composed of three stages, which can be expressed by the J-M-A equations individually. However, the parameter n related to the mode of nucleation and growth is somewhat different in the first and second stages of the two steels, and the same in the third stage for both the steels corresponding to the nucleation Of retained austenite.     

16MnCr5钢锭表层凝固及冷却过程中组织转变规律研究

对１６ｎＣｒ５钢锭表层凝固及冷却过程中的组织转变规律进行了分析,结果表明,钢锭表层我晶转变的不完全性对随后的组织转变有显著的影响,并形成了不均匀铁组织分布。     

Enhancing ductility of the Al-Si coating on hot stamping steel by controlling the Fe-Al phase transformation during austenitization

In this study,austenitizing heat treatment before hot stamping of Al-10%Si coated boron steel is first investigated through environment scanning electron microscopy(ESEM)equipped with energy dispersive x-ray analysis(EDAX).The cracking behavior of the coating was evaluated using Gleeble 3500,a thermo-mechanical simulator under uniaxial plastic deformation at elevated temperatures.The extent and number of cracks developed in the coating were carefully assessed through an optical microscope.The coating layer under hot-dipped condition consists of an Al-Si eutectic matrix,Fe2Al7Si,Fe3Al2Si3 and Fe2Al5,from the coating surface to the steel substrate.The coating layer remains dense,continuous and smooth.During austenitization,the Al-rich Fe-Al intermetallics in the coating transform to more Fe-rich intermetallics,promoted by the Fe diffusion process.The coating finally shows the coexistence of two types of Fe-Al intermetallics,namely,FeAl2 and FeAl.Microcracks and Kirkendall voids occur in the coating layer and diffusion zone,respectively.The coating is heavily cracked and broken into segments during the hot tensile tests.Bare steel exposed between the separate segments of the coating is oxidized and covered with a thin FeOx layer.The appearance of the oxide decreases the adhesion of the Al-Si coating.It is found that the ductile FeAl is preferred as a coating microstructure instead of the brittle FeAl2.Therefore,the ductility of the Al-Si coating on hot stamping boron steel could be enhanced by controlling the ductile Fe-rich intermetallic phase transformations within it during austenitization.Experiments indicate that a higher austenitizing temperature or longer dwell time facilitate the Fe-rich intermetallics transformation,increasing the volume fraction of FeAl.This phase transformation also contributes to reducing the crack density and depth.     

Deep-cryogenic-treatment-induced phase transformation in the Al-Zn-Mg-Cu alloy

An aluminum alloy (Al–Zn–Mg–Cu) subjected to deep cryogenic treatment (DCT) was systematically investigated. The results show that a DCT-induced phase transformation varies the microstructures and affe...     

钢中贝氏体相变热力学

应用综合理论分析的方法研究了钢中贝氏体相变热力学.指出以往的KRC,LFG模型不适于贝氏体相变驱动力的计算.在进行相变热力学分析的基础上,依据γ→αB γ1→BF γ1转变机制设计了新的计算模型,并估算了Bs温度下相变阻力为105 J/mol.指出相变不仅与驱动力有关,而且取决于原子扩散能力.在贝氏体上部温度区,可以依靠界面扩散进行台阶长大;在460 ℃以下的某一段温度,可能以原子热激活跃迁无扩散机制进行贝氏体铁素体形核-长大过程;在Ms点稍上一段温度,可能以切变方式进行.     

钒和钼对微合金化贝氏体钢第二相析出的影响

利用热模拟试验机Gleeble-3800,热模拟试验研究了V、Mo、V＋Mo等元素、加热温度、保温时间对微合金化贝氏体钢中第二相析出的影响.结果表明,Nb、V、Ti、Mo的复合加入有利于第二相的析出,加热温度和保温时间对析出量的影响较小.     

块状转变与钢中贝氏体相变的亲缘关系——再论贝氏体相变的切变扩散整合机制

应用JEM-2010高分辨电镜和Quanta-400型环境扫描电镜,运用试验与综合分析的方法,研究了纯铁的块状转变和钢中的贝氏体相变,通过对相变的形核、长大,贝氏体亚单元和组织的形成的综合研究和分析,认为贝氏体相变与块状转变存在亲缘关系.依靠随机涨落,形成贫碳区,贝氏体铁素体在贫碳的奥氏体中形核.Fe原子和替换原子通过热激活跃迁、界面扩散或切变等方式,重复产生亚单元.在亚单元边界处,富碳奥氏体析出碳化物或成为残留奥氏体.贝氏体相变机制具有过渡性,即切变扩散整合机制.     

Martensite transformation induced by deformation and its phase electrochemical behavior for stainless steels AISI 304 and 316L

The martensite transformation induced by tensile elongation and its effect on the behavior or phase electrochemistry of AISI 304 and 316L in 3.5% NaCl solution were studied.The results show that the content of α′-martensite in stainless steel 304 increases with the true strain,As α′-martensite content increased.freee corrosion potential and pitting potential of stainless steel 304 in 3.5% NaCl solution appeared the change trend of a minimum.It was also found that pitting nucleated preferentially at the phase interfaces between martensite and austenits,There exsted apparent differnece between electrochemical properties of austenite and of martensite for stainless steel 304 and 316L in 3.5% NaCl solution.     

低碳钢钢锭急冷层的相变及其对红送裂纹的影响

研究了德ｎＣｒ５齿轮钢锭急冷层的相变,测定了临界点和ＣＣＴ图,发现急冷层形成时,高温δ铁素体在包晶转变时有剩余,其周围包着奥氏体,在钢锭快冷和再加热过程中有独特的组织转变过程和形态,这种组织易于在相变应力下产生显微裂纹,在宏观内应力作用下可能促发钢锭红送裂纹。     

T8Mn钢株光体连续冷却转变动力学研究

利用定量金相法测得T8Mn钢以 1℃ /min冷速连续冷却转变的动力学曲线 应用Formastor Digital膨胀仪测得T8Mn钢在不同冷速下连续冷却转变的动力学曲线 并利用BASIC软件对曲线进行线性回归分析 ,得到动力学转变的数学模型     

WC-Co涂层磨削过程中的温度与相变

针对WC-Co涂层在磨削中磨削温度会引起相变,进而导致磨削缺陷的问题,以DMU70V数控铣床为平台进行WC-Co涂层磨削实验,利用K型热电偶和DGF40N光纤式红外测温仪测量磨削温度,借助x-射线衍射仪分析磨削前后WC-Co涂层物相组成.实验结果表明,利用热电偶测得的磨削温度与根据磨削过程中WC-Co涂层物质相变推测得到的磨削温度相差较大,利用WC-Co涂层物质相变推测的磨削最高温度与DGF40N光纤式红外测温仪测得的磨削最高温度一致,说明可以利用WC-Co涂层物质相变来推测磨削最高温度,为一些不能直接测量磨削温度的场合提供了新方法.WC晶粒在WC-Co涂层干磨削时大多异质生核,磨削后产生的WC晶粒粒度大,从而导致WC-Co涂层的强度下降,WC-Co涂层不宜干磨削.     

Effect of controlled rolling on the martensitic hardenability of dual phase steel

The C-Mn and C-Mn-Nb steels were thermo-mechanically processed to develop dual phase steel and to study the effect of controlled rolling on the martensitic hardenability of austenite. The steel specimens were intercritically annealed at 790°C,rolled at that temperature to the reductions of 10%,23%,and 47% and immediately cooled at different rates. Quantitative metallography was used to construct the microstructure map,which illustrated that increasing deformation progressively reduced the proportion of new ...     

Phase transformation and reduction kinetics during the hydrogen reduction of ilmenite concentrate

The reduction of ilmenite concentrate by hydrogen gas was investigated in the temperature range of 500 to 1200°C.The microstructure and phase transition of the reduction products were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),and optical microscopy(OM).It was found that the weight loss and iron metallization rate increased with the increase of reduction temperature and reaction time.The iron metallization rate could reach 87.5% when the sample was reduced at 1150°C for 80 min.The final phase constituents mainly consist of Fe,M 3 O 5 solid solution phase(M=Mg,Ti,and Fe),and few titanium oxide.Microstructure analysis shows that the surfaces of the reduction products have many holes and cracks and the reactions take place from the exterior of the grain to its interior.The kinetics of reduction indicates that the rate-controlling step is diffusion process control with the activation energy of 89 kJ·mol-1.     

Reverse Transformation Behavior of TiNi Shape Memory Alloys Prestrained in the Parent Phase

1 IntroductionShape memory alloys (SMAs) prestrained at a tem-perature belowAs(the reverse martensitic transformationstartingtemperature) can generate a large stress or me-chanical energy when constrainedly heated at aboveAf(the reverse martensitic transformation finishing tempera-ture) ,therefore they are regarded as one of the most im-portant actuatorsinsmart composites[1-4].The relationshipbetweenthe prestrain level and the reversible martensitictransformationof TiNi SMAs has beenstudie…     

Laser-induced phase transformation in chalcogenide glasses investigated by micro-Raman spectrometer

A 488 nm continuous wave （CW） laser was employed in Raman spectrometer to both induce and characterize phase transformation in chalcogenide glasses. Laser-induced Raman inactive changes, structural evolution, and crystallization were observed at laser-irradiated region in GeS2-Sb2S3 glasses. The composition dependence of laser-induced phase transformation was discussed in terms of thermal stability and microstructural modification. It is strongly suggested from these results that fabrication of passive and active chalcogenide glass waveguides, such as refractive index change and nonlinear optical crystal line, is controllable by selecting appropriate glass composition, and convenient by using common CW lasers.