脉冲磁场处理非晶合金产生的纳米晶化相的磁伸性质

低频脉冲磁场处理工艺,使非晶薄带Fe78Si9B13产生纳米晶化,析出α-Fe(Si)纳米相,形成α-Fe(Si)纳米晶与剩余非晶的双相纳米合金。穆斯堡尔谱分析,随着脉冲磁场的强度提高,双相纳米晶合金的晶化相体积分数增加。纳米晶化相α-Fe(Si)的磁致伸缩系数λcs为-1.287×10-4～-1.345×10-4。控制晶化相体积分数,可以使双相纳米晶合金的有效磁致伸缩系数λes最小,有利于提高双相纳米晶合金的软磁性能。     

低频脉冲磁场致Co60.15Fe4.35Si12.5B15非晶合金纳米晶化的GMI

采用低频脉冲磁场致Co60.15Fe4.35Si12.5B15非晶合金纳米晶化,晶化过程温升小于5℃,有效避免了材料变脆,获得了优于常规等温退火的纳米晶软磁性能。从实验中观察到较大的GMI效应,且最佳驱动电流频率为2MHZ,横向磁各向异性场为0．9kA／m。     

Fe-Si-B-Nb-Cu-Zr非晶（纳米晶）合金的磁性机理研究

采用单辊甩带法制取了Fe-Si-B-Nb-Cu-Zr非晶合金薄带。利用X射线衍射仪（XRD）、差示扫描量热法（DSC）和振动样品磁强计（VSM）等手段对非晶态和晶化后的薄带的微观结构和磁性能进行了表征和测试,研究了Fe-Si-B-Nb-Cu-Zr合金中磁性能随着Zr含量以及退火温度变化的磁性机理。结果表明,在铸态Fe-Si-B-Nb-Cu-Zr非晶合金中,饱和磁感应强度Bs随Zr含量的增加而减小,矫顽力Hc随Zr含量的增加而增大。经过退火处理后的Fe-Si-B-Nb-Cu-Zr合金的饱和磁感应强度变化不大,但矫顽力随着退火温度的升高先减小后增高,矫顽力在510℃退火时达到最小值,但随着温度增加矫顽力进一步增大。在510℃退火时纳米晶粒与非晶相之间的体积比达到最佳,有效各向异性〈K〉最小,软磁性能最好。     

利用直流高压电场使非晶态合金纳米化的研究

利用直流高压电场处理非晶态合金使之纳米化的研究。非晶态合金Fe73.5Cu1Nb3Si13.5B9在低于初始晶化温度140℃以下，由于高压电场的作用发生晶化，析出大小为2－10nm的α-Fe(Si)晶粒，延长处理时间，晶化效果好，晶粒数明显增多。     

Fe75Cr12.5Mo12.5合金非晶/纳米晶化过程的分子动力学模拟

为模拟Fe75Cr12.5Mo12.5合金非晶/纳米晶化的整个过程,采用分子动力学方法,通过动力学弛豫、淬火和退火处理得到了Fe75Cr12.5Mo12.5合金的非晶/纳米晶态结构.采用径向分布函数(radius distribution function,RDF)和X线衍射图(X-ray diffraction,XRD),分析了模拟过程中各阶段的原子结构.结果表明:Fe75Cr12.5Mo12.5合金的非晶和纳米晶形成能力较强,添加非金属元素能进一步提高非晶形成能力.分子动力学模拟技术为铁基非晶/纳米晶的成分配比和工艺选择提供了理论依据.     

Fe-B非晶合金的等温晶化动力学研究

为研究Fe85B15非晶合金等温条件下晶化的形核、长大及碰撞等动力学机制,采用差热扫描量热仪(DSC)对未经过和经过预热处理的该非晶合金在不同温度下进行等温实验,用X射线衍射仪和透射电子显微镜分析其晶化前后的物相组成和显微结构.该合金等温晶化后为层片状分布的α-Fe和Fe3B两相.运用解析相变模型结合碰撞模式判断,对所...     

Fe-Si-B 非晶态合金的晶化相

采用透射电子显微镜试样倾转法,对非晶态合金Ｆｅ７３Ｓｉ３Ｂ２４的晶化相进行了研究分析,得出Ｆｅ７３Ｓｉ３Ｂ２４在不同温度下含有（１）Ｆｅ３Ｂ亚稳相;（２）Ｆｅ２Ｂ相。     

非晶态合金 Fe73Si3B24 的晶化研究

对非晶态合金Ｆｅ７３Ｓｉ３Ｂ２４的晶化过程进行了探讨采用差热分析方法测定了晶化温度;用Ｘ－射线衍射方法粗略了解了晶化析出相;并用电镜观察了晶化形貌     

分子动力学模拟Ti-Al合金非晶的形成与晶化

用分子动力学方法模拟了Ti-Al合金非晶的形成与晶化过程,非晶合金采用从熔融态淬火至室温的方法获得。通过对不同冷却速率淬火过程的模拟,得到了不同合金成分的非晶转变冷速,表明40-90 at%Al的合金非晶形成能力强,临界冷却速率低。构型分析表明：非晶合金主要由二十面体团簇和初晶团簇构成,非晶退火晶化的微观机理研究说明晶化的过程实际上是体系缺陷和二十面体团簇的数量降低、初晶数量和体积增大的过程。     

梯度功能材料的体积分数和物性系数的研究状况

介绍了国外有关梯度功能材料的体积分数和物性系数问题的研究状况,并对其研究特点进行了评述.     

水泥基复合材料界面过渡区体积分数的定量计算

为了计算水泥基复合材料的界面过渡区体积分数,采用最邻近表面分布函数和骨料比表面积2种方法,结合实际骨料的筛分曲线,给出了界面过渡区体积分数定量关系式．结果表明：单位体积水泥基复合材料中,当骨料的体积分数〈0．5,界面厚度〈50μm时,2种方法计算的误差约为10％;界面区厚度越小,2种方法计算的误差也越小．     

球状沉淀相微粒体积分数的计算

通过建立数学模型,推导出球状沉淀相微粒表观体积分数和真实体积分数的计算公式,并经实验证实了公式的可靠性。     

Mechanical model for yield strength of nanocrystalline materials under high strain rate loading

To understand the high strain rate deformation mechanism and determine the grain size,strain rate and porosity dependent yield strength of nanocrystalline materials,a new mechanical model based on the deformation mechanism of nanocrystalline materials under high strain rate loading was developed.As a first step of the research,the yield behavior of the nanocrystalline materials under high strain rate loading was mainly concerned in the model and uniform deformation was assumed for simplification.Nanocrystalline materials were treated as composites consisting of grain interior phase and grain boundary phase,and grain interior and grain boundary deformation mechanisms under high strain rate loading were analyzed,then Voigt model was applied to coupling grain boundary constitutive relation with mechanical model for grain interior phase to describe the overall yield mechanical behavior of nanocrystalline materials.The predictions by the developed model on the yield strength of nanocrysatlline materials at high strain rates show good agreements with various experimental data.Further discussion was presented for calculation results and relative experimental observations.     

磁性材料的研究和发展趋势

介绍了磁性材料的种类和发展过程,并在此基础上阐述了磁性材料的研究进展、性能及应用,展望了其发展趋势和今后的研究开发的重点.     

Computation and measurement for distributions of temperature and soot volume fraction in diffusion flames

A combined computational and experimental investigation to examine temperature and soot volume fraction in coflow ethylene-air diffusion flames was presented.A numerical simulation was conducted by using a relatively detailed gas-phase chemistry and complex thermal and transport properties coupled with a semi-empirical two-equation soot model.Thermal radiation was calculated using the discrete ordinates method.An image processing technique and a decoupled reconstruction method were used to simultaneously me...     

Rate dependent rheological stress-strain behavior of porous nanocrystalline materials

To completely understand the rate-dependent stress-strain behavior of the porous nanocrystalline materials,it is necessary to formulate a constitutive model that can reflect the complicated experimentally observed stress-strain relations of nanocrystalline materials.The nanocrystalline materials consisting grain interior and grain boundary are considered as viscoplastic and porous materials for the reasons that their mechanical deformation is commonly governed by both dislocation glide and diffusion,and pores commonly exist in the nanocrystalline materials.A constitutive law of the unified theory reflecting the stress-strain relations was established and verified by experimental data of bulk nanocrystalline Ni prepared by hydrogen direct current arc plasma evaporation method and hot compression.The effect of the evolution of porosity on stress-strain relations was taken into account to make that the predicted results can keep good agreements with the corresponding experimental results.     

Microstructure refinement and magnetic properties enhancement of nanocrystalline Nd_(12.3)Fe_(81.7)B_(6.0) ribbons by addition of Zr

Effects of Zr addition and annealing treatment on the formation, microstructure and magnetic properties of Nd12.3Fe81.7?xZrxB6.0 (x=0―3.0) ribbons melt-spun and annealed have been systematically investigated by means of vibrating sample magnetometer (VSM), differential scanning calorimeter (DSC), X-ray diffraction (XRD), and high resolution scanning electron microscopy (HRSEM). Phase analysis reveals that Nd2Fe14B is single-phase material. It has been found that the intrinsic coercivity Hci of the optimally...     

Self-healing Action of Permeable Crystalline Coating on Pores and Cracks in Cement-based Materials

The self-healing action of a permeable crystalline coating on the porous mortar was investigated by two times impermeability test. Moreover, the self-healing mechanism of cement-based materials with the permeable crystalline coating, was studied by SEM. The results indicate that the permeable crystalline coating not only seals the pores and cracks in mortar during its curing process, but also heals the permeable pathway caused by first impermeability test or cracks produced by freeze-thaw cycles . Therefore, cement-based materials can be improved by the permeable crystalline coating for the self-healing function. SEM images prove that the self-healing function is realized by generating a great quantity of non- soluble dendritic crystalline within the pores and cracks, which prevents the penetration of water and other liquids.     

Microstructure refinement and magnetic properties enhancement of nanocrystalline Nd<Subscript>12.3</Subscript>Fe<Subscript>81.7</Subscript>B<Subscript>6.0</Subscript> ribbons by addition of Zr

Effects of Zr addition and annealing treatment on the formation, microstructure and magnetic properties of Nd_12.3Fe_81.7−x Zr _x B_6.0 (x=0−3.0) ribbons melt-spun and annealed have been systematically investigated by means of vibrating sample magnetometer (VSM), differential scanning calorimeter (DSC), X-ray diffraction (XRD), and high resolution scanning electron microscopy (HRSEM). Phase analysis reveals that Nd₂Fe₁₄B is single-phase material. It has been found that the intrinsic coercivity H _ci of the optimally processed Nd_12.3Fe_81.7−x Zr _x B_6.0 ribbons increases monotonically from 751.7 kA/m for x=0 to 1005.3 kA/m for x=3.0. The remanence polarization J _r and maximum energy product (BH)_max increase first with Zr addition, then slightly decrease with further increasing Zr content. Optimum magnetic properties with J _r=1.041 T, H _ci=887.5 kA/m and (BH)_max=175.2 kJ/m³ have been achieved for the ribbons with x=1.5. The significant improvement of magnetic properties originates from the finer grains of the ribbons by introducing Zr.