铸造-热变形Nd-Fe-B永磁合金显微组织及性能的研究

对铸造NdFeB磁体进行了不同变形温度、不同变形量的热压及压后热处理的实验.研究了不同工艺下磁体的显微组织以及与磁性能的关系.结果表明,NdFeB永磁合金的磁性能和磁体的微观组织有密切关系.铸态组织对制造铸造-热压NdFeB永磁材料具有重要的影响,最终组织晶粒细小、均匀,主相被富Nd相薄层包围,晶界平直,高C轴取向,可以获得高磁性所要求的微观组织.     

微观结构调整对烧结Nd-Fe-B永磁氧化特性和磁性能的影响

采用放电等离子烧结技术(SPS)制备了新型Nd-Fe-B磁体,采用传统烧结工艺制备了相同成分的磁体.测量了磁体在不同温度下的氧化动力学、不可逆损失以及氧化前后磁性能的变化.利用扫描电子显微镜分析了磁体氧化前后的显微组织结构.结果表明,高温氧化后SPS磁体的磁性能损失低于传统磁体.显微组织观察表明新型磁体具有独特的显微组织特征:主相Nd₂Fe₁₄B晶粒细小、均匀;富钕相在主相晶粒边界上分布较少,主要集中在三角晶界处.这种组织结构有效地抑制了磁体沿富钕相发生晶间氧化的过程,因此磁体具有良好的耐氧化性能.     

Effect of Dy substitution on the microstructure and magnetic properties of nanograin Nd-Fe-B single-phase alloys

Nanocrystalline single-phase alloys with the nominal compositions (at%) of Nd12.3-xDyxFe79.7Zr0.8Nb0.8Cu0.4B60 (x=0, 0.5,1.5, and 2.5) were prepared by melt-spinning and subsequent annealing. X-ray diffraction analysis shows that the as-spun ribbons were mainly com-posed of the amorphous phase. A slight content of Dy stabilizes the amorphous phase during annealing treatment. The grain size becomes smaller and the coercivity of the annealed ribbon is gradually improved with the increase of Dy content. Excessive Dy is harmful to the re-manence. It is found that no intergranular phase exists between the grains by high-resolution transmission electron microscopy, and the grain boundaries are crystallographically coherent in the optimally annealed sample. The optimum magnetic properties of remanence (Jr=1.09 T), coercivity (Hci=1048 kA/m), and maximum magnetic energy product ((BH)m=169.5 kJ/m3) are obtained from the x=0.5 ribbon in a post heat-treated state (700℃, 10 min).     

Microstructure and properties of high emissivity coatings

A new coating on lining in industrial furnace for energy saving has been developed. Properties and microstructure of the coatings were revealed by emissivity instrument,X-ray diffraction (XRD),transmission electron microscope (TEM) and scanning electron microscope (SEM),respectively. The result indicates that the emissivity of coatings is higher than 0.90 and the thickness of coatings is about 200 μm. ZrO2,Cr2O3 and SiC in the coating benefit practical applications of coatings at high temperature with du-ra...     

Microstructure and Properties of Activated Slag Cement

Activation of the slag cement was performed using a composite activator. Experimental results show that the performance of the cement is remarkably improved. The fineness and specific surface area of the cement are increased by 23.7% and 1.4% , and 3d flexural strength and compressive strength are enhanced by 20.9% and 22.9%, respectitely. Microstructure and phase composition of the hydrates were analysed by X-ray diffraction( XRD ) and scanning electron microscopy( SEM ). The results indicate that Ca(OH)2 in the hydrates decrease obvioasly. The morphology of the other hydrates appears to be flocculent, with a dense structure. The improvements of the properties is related to the microstructural changes.     

喷射成形沉积坯组织性能分析

利用金相显微镜和扫描电镜对GCr15喷射成形试样的疏松、显微组织进行了分析,采用能谱分析法对试样中元素含量及分布进行了分析.提出了改进显微组织和性能的方法.     

Ti-B-C-N粉末烧结的微观组织及其性能

以Ti-B-C-N四元相陶瓷粉末为实验材料,采用真空热压烧结和放电等离子烧结(SPS)工艺对其进行烧结,真空热压烧结和放电等离子烧结温度分别为1900℃和1450℃,烧结压力分别为20 MPa和40 MPa,保温时间分别为1h和3min。使用X射线衍射仪分析试样物相组成,扫描电子显微镜观察试样表面微观形貌和断口形貌,并测试了烧结试样的硬度和抗弯强度。结果表明:真空热压烧结和放电等离子烧结块体的主要生成相为TiB2相和TiCN相,相对密度分别为97.40%和93.06%,热压烧结试样致密度高,颗粒尺寸大,放电等离子烧结试样孔隙较多,晶粒尺寸小;抗弯强度分别为259.98 MPa和335.17 MPa;弹性模量分别为89.11GPa和162.92GPa;洛氏硬度分别为78.8和84.9;放电等离子烧结试样表现出较好的力学性能。     

Microstructure and Properties of CePO4 Ceramic

Cerium phosphate powders were synthesized by direct solid liquid reaction of cerium dioxide and phosphate acid at the Ce ： P ratio of 1 ： 1. Phase-pure and fine grain size CePO4 powers could be obtained by calcining the as received powders at the temperature higher than 600 ℃ . It is demonstrated that the grain size and morphology of the CePO4 powders were calcined at various temperatures. An interesting layered crystal structure and a series of microcracks that cross and occur along the extrusion stress direction on the extruded surface inside CePO4 were observed. The ductility and machinabililty of CePO4 ceramic are attributed to the layered structure. Continuous machining debris was observed on the turned surface.     

时效态Al-Zn-Mg-Cu-Zr-Sc合金的组织与疲劳性能

为了研究时效处理对Al-7.2Zn-2.5Mg-1.5Cu-0.08Zr-0.12Sc合金的组织与疲劳性能的影响,利用透射电子显微镜对合金的显微组织进行了观察分析,并针对不同时效状态的合金进行了低周疲劳实验.结果表明,经过150℃×6 h时效处理后,合金晶内析出相较少,晶界无析出相;经过150℃×36 h时效处理后,合金晶内析出相较为细小,并呈弥散分布,同时晶界析出断续分布的平衡相,并存在晶界无析出带;经过150℃×48 h时效处理后,合金的析出相均已长大,且晶界无析出带发生宽化.经过150℃×36 h时效处理后的合金,表现出了较高的循环变形抗力与较长的低周疲劳寿命;不同时效状态合金的塑性应变幅、弹性应变幅与载荷反向周次之间,以及循环应力幅与塑性应变幅之间均呈线性关系.     

掺盐沥青胶浆低温流变及粘附特性

为探究盐分对沥青胶浆低温流变及粘附特性的影响规律,采用盐颗粒以体积比1∶1替代矿粉的沥青胶浆制备方法,通过弯曲梁流变试验(BBR)研究不同掺盐沥青胶浆在30 d与120 d龄期下的低温流变特性,并构建相应的Burgers模型,分析盐分对沥青低温粘弹特性的影响;通过接触角试验,得出沥青表面能参数,评价不同沥青胶浆粘附特性;借助扫描电镜(SEM)和红外光谱(FTIR)手段,探究掺盐沥青胶浆微观作用机理。结果表明:相较于基质沥青,不同种类掺盐沥青胶浆随着龄期的增加,低温流变性能不断降低;经120 d龄期后,沥青接触角明显增大,掺盐沥青胶浆表面能降低,粘附性劣化;盐分颗粒溶析及其盐老化效应,是导致掺盐沥青胶浆性能劣化的主要诱因。     

Microstructure,mechanical properties and magnetic properties of FeCoNiCuTiSi_x high-entropy alloys

The microstructure, mechanical properties and magnetic properties of FeCoNiCuTiSi_x(x=0, 0.05, 0.1, 0.2, 0.4 and 0.5) highentropy alloys were studied in detail in the present paper. The crystal structure changes from FCC+Laves to FCC+BCC+Laves phases, as the Si content increases. Cu is more segregated with the increase in Si content, which can be explained from a thermodynamic point of view. The FeCoNiCuTi high-entropy alloy has good compression mechanical properties, and the fracture strength, fracture strain, and Vickers hardness are 1584.2 MPa, 3.3% and 483.2 HV, respectively. However, the plasticity of the alloy decreases slightly as the Si content increases. The highest fracture strength obtained in this study is 1841.7 MPa at x=0.1.     

Effect of optimal aging treatment on magnetic performance and mechanical properties of sintered Nd-Fe-B permanent magnets

The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged Nd Fe B magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy(FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged Nd Fe B magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd_2Fe_(14)B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.     

铸造热变形Nd-Fe-B永磁合金铸锭组织的研究

Nd-Fe-B铸锭组织对于制造热变形Nd-Fe-B永磁材料具有重要的影响.采用型号为ZEISS25CA的金相显微镜和型号为KYKY1000B的扫描电镜对铸造热变形Nd-Fe-B永磁合金的铸锭组织进行了研究.结果表明,通过改进冷却方式,Nd2Fe14B晶粒明显细化;固溶处理可以消除α-Fe.为进一步改进Nd-Fe-B铸锭的生产工艺进而最终获得高性能的热变形Nd-Fe-B永磁体提供了理论依据.     

AlFeCuCrCoMo_x系高熵合金的组织性能

为了研究AlFeCuCrCoMo_x系高熵合金的组织性能,利用等离子弧堆焊方法制备了AlFeCuCrCoMo_x系高熵合金,并测试了其硬度、耐磨性与热膨胀性能.结果表明,高熵合金组织为枝晶和枝晶间组织.当Mo含量较低时,高熵合金主要组织为单一BCC结构.随着Mo含量的增加,其组织逐渐转变为BCC+FCC结构.当Mo含量为1. 5 mol时,高熵合金重新转变成简单BCC结构.随着Mo含量的增加,高熵合金的硬度和磨损量总体上呈现先升高后降低的趋势.当Mo含量为1. 5 mol时,高熵合金的硬度和磨损量达到最大.     

Microstructure and cementitious properties of calcined clay-containing gangue

To investigate the optimum calcination temperature and cementitious properties of gangue, the microstructure of clay-containing gangue calcined at different temperatures was analyzed by X-ray diffraction (XRD), infrared spectroscopy (IR), and magnetic angle spinning nuclear magnetic resonance (MAS NMR). The results show that the structure of kaolinite in the gangue sample calcined at 500°C is destroyed. The XRD spectra show the disappearance of illite at about 800°C and the formation of mullite at about 100...     

Microstructure and properties of sputtered thermal barrier coatings

A 3 kW radio frequency (RF) magnetron-sputtering unit was used to produce zirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlY bond coat layer by cathodic arc deposition. The NiCrAlY coating surface was shot-peened, and the residual stress in the bond coat layer and the effects of heat treatment on the residual stress are presented. After shot peening porosities and microgaps disappear in the NiCrAlY bond coat, the whole depth profile is residual compressive stress. Coarseness tests show that the roughness value (Rz) decreases from 16.4 to 3.3 μm. The microstructure and phase composition of the coatings were investigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that tho/NiCrAlY bond coat is composed of γ and Cr phases, and the Al2O3 scales are formed near the interface between the ZrO2 ceramic layer and the NiCrAlY bond coat. No degradation occurred to RF sputtered ceramic coatings after oxidating at 1150℃ for 100 h, heating at 1150℃ for 5 min and then air-cooling for 500 thermal cycles.     

Microstructure and properties of novel polarization maintaining fiber

An improved type of elliptical jacket polarization maintaining fiber was developed by using a modified chemical vapor deposition method with special treatment. Different from conventional elliptical jacket, the shape of the stress jacket was transmuted. The cross-section of fiber consists of 5 layers: substrate, outer cladding, stress jacket, inner cladding and core. The cross sectional component distribution was investigated by electron probe microscopy and energy dispersive spectrum. The finite element method was used to calculate the stress birefringence.Based on the analyses of the microstructure, the technological process is improved. The temperature cycling test of the fiber wound into gyroscope coils was performed. The results show that the fiber possesses superior performance at high and low temperatures compared with other fibers. The high homogeneity is achieved by well-controlled modified chemical vapor deposition process. A homogeneous length of 8 km fiber is obtained. With advantages in homogeneity and length, the fiber has great potential in applications such as fiber gyroscopes, fiber hydrophone and other optical fiber sensors.     

FeTiNbMoW高熵合金的组织和性能

为了研究一种能够吸收γ射线的含W合金的性能,按照等摩尔比设计了一种FeTiNbMoW五组元高熵合金.利用X射线衍射仪、扫描电子显微镜、能谱仪、显微硬度计、密度仪和万能力学试验机对合金的晶体结构、微观组织、成分、硬度、密度和压缩性能进行了分析.结果表明,FeTiNbMoW高熵合金组织由简单BCC固溶体基体和分布其上的少量金属间化合物组成.BCC结构的实际晶格常数为0.315 5 nm,组织形貌为典型枝晶组织.枝晶硬度和枝晶间硬度分别为830.05和793.04 HV.合金的实测密度为10.7 g/cm3,略高于其理论值10.21 g/cm3.室温下合金的抗压强度和对应塑性应变分别为604 MPa和3.19%.合金呈粉末性断裂,其断裂机制为解理断裂.     

低温染色对山羊绒纤维物理性能的影响

比较了低温染色和常规染色的浅、中、深色山羊绒纤维的染色牢度,利用电子单纤维强力仪测试其强伸性能,并利用扫描电子显微镜比较染色前后纤维的表面形态．实验结果表明,山羊绒纤维经过低温染色工艺,单纤维平均断裂强力与断裂伸长率明显提高,浅色和中色染色色牢度与常规染色工艺的色牢度接近,但在染深色时色牢度有所下降,低温染色工艺中纤维鳞片表面的损伤比常规染色纤维小,表明低温染色工艺可以减轻染色过程中对山羊绒纤维的损伤,尤其是深色染色更为明显,从而提高山羊绒后续产品的服用性能．     

Effect of Cu doping and annealing treatment on the microstructure and magnetic properties of nanocrystalline single-phase Nd-Fe-B alloys

The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Nd12.3Fe81.7-xCuxB6 (x=0-1.2) ribbons melt-spun and annealed were systematically investigated by the methods of vibrating sample magnetometer (VSM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Optimum magnetic properties were achieved by annealing melt-spun Nd12.3Fe81.5Cu0.2B6 ribbons at 550°C for 15 min, which only contained Nd2Fe14B phase. The remanence, coercive force, and maximum ...