超细晶钢在不同温度下塑性变形机制的研究

将晶粒尺寸分别为2、7、80μm的微合金钢在295～973K温度范围内进行单轴拉伸试验，通过对比分析3种不同晶粒尺寸微合金钢的工程应力一应变曲线及微观组织，讨论了超细晶粒钢在不同温度下的塑性变形机制。在295～473K范围内，3种不同晶粒尺寸微合金钢的塑性变形机制以位错运动为主；在573K，晶界滑动开始在超细晶粒钢中出现，在973K，成为塑性变形的主导机制；粗晶粒钢在573～973K范围内以位错运动为塑性变形的主要机制。     

应变诱发铁素体相变对低碳钢晶粒细化的影响

研究了在奥氏体低温区变形时显微组织的变化,并测试了其变形抗力。结果表明：在Ar3以上温度变形会产生应变诱发铁素体相变,使变形抗力下降。通过降低变形温度,铁素体晶粒得到细化。     

液相还原法制备超细铜粉的研究进展

超细铜粉由于其特殊的性能,因而应用范围很广泛。其制备的工艺也引起了广泛的关注,其中液相还原法由于其特殊的优点,故研究的较多。文中阐述了液相还原法制备超细铜粉的工艺的研究进展以及铜粉表面改性的工艺,并提出了问题及对未来的展望。     

Effect of Deformation on Order-Disorder Phase Transformation in Cu-Zn Alloy

The phase transformation temperature of ordered β' to disordered β in the Cu-Zn alloy was tested by DSC. The transformation activation energy was calculated and the effect of deformation of the phase transformation was discussed. The results show that the phase transformation temperature and activation energy of ordered β' to disordered β in the Cu-Zn alloy can be decreased going through deformation, and the phase transformation time can be also decreased. As a result, the order-disorder phase transformation occurs more easily.     

Effect of Niobium on Isothermal Transformation of Austenite to Ferrite in HSLA Low-Carbon Steel

Using thermomechanical simulation experiment,the kinetics of the isothermal transformation of austenite to ferrite in two HSLA low-carbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation.The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism,wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation,whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs,wherein,the nucleation rate of ferrite in the initial stage of transformation is low,and in the second stage,the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete.Using carbon extraction replica TEM,niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite.The mechanism of the effect of niobium on the isothermal transformation was discussed.     

中碳钢形变及冷却过程中的组织演变

热模拟单向压缩下,中碳钢形变温度低于Ad3（786℃）点时,析出形变诱导铁素体（DIF）,DIF量随形变温度降低而提高;在低于750℃形变时,DIF量远高于平衡态铁素体含量54％。DIF析出时碳原子高度富集在铁素体晶界和铁素体／奥氏体界面。形变后在低于A1（719℃）温度等温或控冷过程中。过冷奥氏体将发生不同类型的转变：高于Ad3形变试样中,奥氏体转变为铁素体＋片层状珠光体;低于Ad3点但高于Ar3（645℃）点形变时,未转变奥氏体转变为铁素体＋片层状珠光体＋晶界渗碳体;稍高于Ar3点形变时,将获得铁素体＋弥散渗碳体的球化组织。     

Nb的析出对变形诱导铁素体相变的影响

通过Gleeble2000热模拟实验机，研究了X65管线钢中Nb在变形奥氏体中的析出状态对变形诱导铁素体相变（DIFT）的影响。试验结果表明，在奥氏体临界区变形时，第一道次变形后，随变形后等温时间延长，诱导铁素体量变化不大。等温时间达120S时，变形奥氏体仍未发生再结晶。在道次间随时间延长，Nb的析出量增加，第二道次变形后诱导的铁素体也显著增加。微合金元素Nb通过碳氮化物的析出作用促进变形诱导铁素体相变。     

X70管线钢连续冷却过程的相变研究

以两种微合金化方式(Nb、V、Ti和Nb、V、Ti、Mo)的X70管线钢为研究对象,在MMS-200热模拟试验机上进行了双道次轧制工艺模拟试验,研究不同卷取温度、冷却速度对X70显微组织的影响.结果表明,随着卷取温度的降低及冷速的提高,金相组织细化.卷取温度在520℃、冷速在15℃/s左右可以得到较为理想的针状铁素体组织.Nb、V、Ti微合金化管线钢,当冷却速度为15℃/s时,带状组织完全消失.     

钒微合金化低碳钢多道次变形过程中的组织演变

采用热模拟实验研究了钒微合金化低碳锰钢(0.1%C-1.0%Mn)奥氏体化后在860~740℃范围内进行多道次变形过程中的组织演变,考察了变形和微合金元素V对铁素体相变的影响.结果表明,在多道次变形过程中,部分奥氏体通过形变诱导相变转变为铁素体;高温区的道次间隔期间部分形变诱导铁素体发生向奥氏体的逆相变;随变形温度降低,道次间隔期间有变形奥氏体向铁素体的亚动态相变发生。微合金元素V抑制形变诱导铁素体相变的进行,阻碍铁素体晶粒长大,起到细化晶粒的作用.     

Phase Composition of Electrospark Tungsten Carbide-Based Coatings after Heating and Isothermal Soaking

A study of phase formation on electrospark coatings with WC Co Cu electrodes on R6M5 high-speed steel during isothermal heat treatment at the operating temperature of the coating. Copper tungstate CuWO ₄has been found to form, with its crystal lattice coherently bound to the basic carbide phase of the coating, tungsten monocarbide, through tungsten semicarbide as intermediary. The results complement the data on phase formation during the application of WC-based coatings and during their subsequent use with sliding friction.     

稀土对16Mn钢等温相变及显微组织的影响

采用金相观察与硬度测量相结合的方法测定了不同稀土含量16Mn钢的TTT曲线,并研究了稀土含量对其等温相变及显微组织的影响.研究表明,随稀土含量的增加,先共析铁素体的晶粒大小及其析出的孕育期减小,完成珠光体相变所需时间和组织中铁素体含量增大;贝氏体形态逐渐由羽毛状向粒状转变.含稀土钢组织中的碳化物具有明显的偏聚现象.本文对这些结果产生的原因进行了讨论.     

氧化锆系的相结构和转变

ZrO2随温度变化，历经单斜，四方和立方三个相系，通过DTA分析和X衍射技术研究低温水合ZrO2和高温ZrO2的相变过程，证实了氧化锆相系变化的特性，表明ZrO2由单斜向四方转变时，产生滞后效应，其温区范围在930-1170℃之间，这是一个可逆的相转变过程，在常温下稳定的只是单斜ZrO2。在ZrO2中添加阳离子可以稳定氧化锆相系，使之在常温下获得稳定的四方面相和立方相ZrO2。用X射线衍射研究了添加阳离子固溶氧化锆的机理和稳定化的作用。还评述了氧化锆三个相结合的特性和它的差异性。     

钒对高氮钢形变诱导相变的影响

通过实验室模拟试验,研究了高氮钒钢的金相组织和形变诱导铁素体体积分数,分析了钒对高氮钒钢变形诱导相变的影响.试验结果表明,钒的加入促进了形变诱导铁素体相变,细化了铁素体晶粒,提高了形变诱导铁素体体积分数.     

等温处理对高级别管线钢晶内铁索体形成的影响

采用热模拟技术,研究700、650、600、550℃等温处理对管线钢晶内铁素体形成的影响以及600℃下钢的组织随等温时间的转变规律。测量不同等温温度处理后钢的维氏硬度,分析钢中诱导晶内铁素体析出的夹杂物的成分。结果表明,由700℃逐渐降低至550℃进行等温处理,钢的硬度先降低后升高,晶内铁素体的数量在650℃时最大;600℃时在原奥氏体晶粒内部,晶内针状铁素体与贝氏体存在竞争关系;由Mg、Al、Ti等元素构成的复合夹杂物可以诱导晶内铁素体形核。     

Formation of Intragranular Ferrite During Isothermal/Thermomechanical Processes in a Medium Carbon V-Ti-N Microalloyed Steel

For a V-Ti-N microalloyed steel with 0.34%C-1.54%Mn,intragranular ferrite (IGF) was obtained in both isothermal austenite decomposition processes and thermomechanical processes simulating the industrial seamless tubing manufacture process.Results show that with decrease of the isothermal temperature in range of 600℃ down to 450℃,not only the morphology of IGF changed from equiaxed to acicular,but also the equiaxed IGF and the acicular IGF were refined.More importantly,it is found that the amount of equiaxed ferrite increased significantly in the thermomechanical process sample water quenched from 550℃ after 800℃ deformation than that in the isothermally treated sample at 550℃ sample without hot deformation.It implies that appropriate controlled deformation with controlled cooling can significantly promote equiaxed IGF formation,and not solely rely on nucleation mechanisms related with inclusions.Hot deformation of austenite without dynamic and complete static recrystallization causes high energy regions,therefore further promotes the nucleation potency of IGF.     

In-Situ High Temperature X-Ray Diffraction Study of Structure and Phase Transformation of Nd-FePt Alloys

The structure and disorder-order transformation of NdxFe60.5-x Pt39.5（x = 0, 0.5, 1.0, 1.5） alloys were investigated in situ by high temperature X-ray diffraction. The results show that the lattice parameter a of disordered γ phase （FCC, Al structure type） and the lattice parameter ratio c/a of ordered γ1 phase （FCT, L10 structure type） increase linearly with increasing Nd concentration, whereas the c/a ratio decreases with increasing temperature. The transition temperature from ordered FCT to disordered FCC decreases with increasing Nd concentration, but for alloys quenched rapidly from γ phase region into ice-water it increases with increasing Nd.     

落球冲击下高铬铸铁磨球中残余奥氏体的形变与相变

用透射电镜和微区Ｘ射线衍射分析了落球冲击后高铬铸铁磨球皮下不同深度残余奥氏体形变和相变情况。发现不同深度发生形变和相变的程度是不同的，在磨球表面最大，随着深度增加形变和相变的程度减小。产生可观塑性变形的深度在５ｍｍ以内，而发生相变的深度可达１０ｍｍ。不同深度相变的机理不同。共晶碳化物在落球冲击下也能发生一定的塑性变形。最后分别讨论了显微组织变形和相变对磨球抗剥落破碎性能的影响。     

Mechanism of Phase Transformation and Formation of Barium Hexaferrite Doped with Rare-Earths in Sol-Gel Process

The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La3 ~ were studied by chemical phase analysis, X-ray diffraction and infrared spectrometry analysis. The experimental results show that phase transformation reactions of FeCO3, Fe2O3 and BaFe2O4, barium hexaferrite and γ-Fe2O3 take place in the heat treatment of gel. While the doping lanthanide ion replace barium ion, an equivalent quantity of Fe^3 are reduced to Fe^2 to maintain the eharge equilibrium.     

Effects of Sm on Phase Transformation in Ni-Mn-Ga Alloys

The effects of small amount additions of Sm on the martensitic transition and magnetic phase transition of polycrystalline Ni-Mn-Ga alloys were investigated. The experimental results show that the Sm doped alloys also undergo a thermal-elastic martensitic transformation and reverse transformation during cooling and heating process and the addition of Sm decreases the martensitic transformation temperature and Curie temperature in different degree respectively. Ni-Mn-Ga alloys of adding Sm still possess Heusler structure, but their crystal lattice parameters are modified slightly. The addition of a proper amount of Sm does not basically decrease Tc of the alloy when avoiding the appearance of second phase. In addition, the doped alloys have favorable toughness because of grain refinement of Sm.