PREPARATION AND MAGNETIC ANISOTROPY OF NANOCRYSTALLINE Fe0.13(CoxNi1-x)0.87FINE FIBERS

以柠檬酸和金属盐为原料, 采用有机凝胶--热还原法制备了纳米晶Fe_0.13(Co_xNi_1-x)_0.87(x=0.20, 0.30, 0.50, 0.80) 微细纤维. 采用FTIR, XRD和SEM等对纤维前驱体和热还原产物的结构、物相和形貌进行了分析; 采用振动样品磁强计 (VSM) 对纤维的磁性进行了 测试. 结果表明: 纤维直径分布在0.3---2 μm之间, 表面光滑, 长径比大, 组成纤维的晶粒尺寸约为34 nm. Fe_0.13(Co_xNi_1-x)_0.87微细纤维表现出明显的磁各向异性, 该性能主要受磁晶各向异性、形状各向异性和静磁相互作用等因素影响.纤维的易磁化方向为其轴向方向, 难磁化方向为径向方向, 所制备的Fe_0.13(Co_0.50Ni_0.50)_0.87纤维的剩磁比M_r/M_s(剩余与饱和磁化强度比)最大, 达到0.48.     

有机凝胶-热分解法制备尖晶石型CoFe2O4纤维

以金属钴盐、铁盐及柠檬酸为原料,采用有机凝胶-热分解法成功制备了尖晶石型的CoFe2O4纤维.通过红外光谱(FTIR)、X射线衍射(XRD)、热重-差热分析(TG-DSC)以及扫描电镜(SEM)等分析手段对凝胶的结构、组成、热分解过程以及热处理产物的形貌进行了表征,并分析了影响凝胶可纺性以及纤维产生缺陷的各种因素.结果表明:在pH值为5.5左右的溶液中金属离子与柠檬酸反应形成具有线性分子结构的[(C6H6O7)4CoFe2]n,由这些线性分子所组成的凝胶显示出良好的可纺性.所制备的尖晶石型CoFe2O4纤维由40～50 nm大小的晶粒组成,纤维直径可小于1 μm,长径比达1×106.通过振动样品磁强计(VSM)测得这种尖晶石型CoFe2O4纤维的饱和磁化强度和矫顽力分别为81.97 A·m2/kg和1041.47×79.6 A/m.     

M型中空钡铁氧体纤维的制备和表征

以柠檬酸、乳酸和金属硝酸盐为原料,采用有机凝胶先驱体转化法制备了中空M型(BaFe12O19)纤维.通过FTIR、TG/DSC、XRD、SEM和VSM等技术对所得纤维进行了表征,并初步探讨了中空纤维的形成机制.结果表明,凝胶的可纺性与其组成和pH值有关,在pH值约等于4.5时,可纺性最好.纤维直径可小于1 μm,长径比可达8×105,组成纤维的晶粒尺寸大都在数十个纳米.中空BaM纤维在室温下的饱和磁化强度为22.5 Am2、Kg,矫顽力为300 kA/m.     

苹果酸溶胶-凝胶法制备氧化铝长纤维(英文)

用硝酸铝、苹果酸为原料,用溶胶-凝胶法制备氧化铝前驱体溶胶。研究了苹果酸、聚乙烯吡咯烷酮(PVP)的加入量对溶胶可纺性能的影响。研究发现:当硝酸铝、苹果酸、PVP的质量比为10:3:1.5时,得到的凝胶纤维长度大于80cm。用热重-差示扫描(TG-DSC)、傅里叶转换红外线光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)分析方法对凝胶纤维和陶瓷纤维进行了表征。凝胶纤维的长度大于80cm。凝胶纤维在1200℃煅烧1h后,物相为α-Al2O3,得到的氧化铝纤维直径均匀、表面光滑,纤维直径为20μm。     

铝合金薄壁筒滚珠旋压成形分析

作为一种连续局部塑性成形工艺,滚珠旋压被应用于制造铝合金薄壁筒形件。介绍了滚珠旋压的基本原理,以塑性力学为基础,分析力学参数对旋压件成形性的影响。实验中通过采用LF2和LY12两种铝合金筒坯,获得金属材料的塑性和屈服强度对旋压件可旋性影响的一般规律。最后研究咬入角对金属材料稳定流动的影响,并通过实验获得了合理的咬入角值。     

新型陶瓷浇口套在低压铸造铝合金轮毂中的应用

在铝合金轮毂低压铸造过程中,浇注系统的设计及材料的选取对铸造过程中的充型及凝固影响重大。对使用陶瓷浇口套与传统金属浇口套的工艺稳定性,进行了对比分析。结果表明,在低压铸造过程中,传统的金属浇口套存在腐蚀快、导热快、铸造工艺难以调整并且波动大、受环境和原料温度影响大等问题;陶瓷浇口套耐腐蚀性强、保温性好、耐高温,能有效地保证补缩通道的温度,最终凝固的冒口部位废料明显减少。     

蛇纹石内氧化效应对铁基金属磨损表面自修复层生成的作用

高性能SiC纤维在耐高温、抗氧化领域有着重要的应用前景,而纤维直径是影响纤维力学性能的主要因素之一。随着纤维直径降低,纤维强度显著升高。利用静电纺丝工艺,结合先驱体热解转化法制备SiC,探索了一种简单、易行的制备亚微米/纳米SiC纤维的方法。由聚碳硅烷(PCS)出发,研究了PCS溶液静电纺丝的工艺参数对纺丝性的影响,PCS原纤维经不熔化、N2中1200℃热处理1h,成功的制备了纤维直径在0.5原2μm之间分布均匀的SiC纤维。     

Alloy Microstructures in Cast Metal Matrix Composites

This article provides some insight into an area that has here-to-fore been ignored, namely, the matrix microstructure of cast metal matrix composites (MMC). Using the Al-4.5% Cu alloy as a model matrix alloy, the factors influencing the cast microstructure are explored on samples reinforced with several types of fibers. The nature of the fibers, their diameter and distribution along with conventional solidification parameters have a profound influence on the matrix microstructure. A full exploration of the relationships between properties, microstructures and processing parameters is required for the optimization of this class of materials.     

Joining stainless steel metal foams

Abstract

Metallic foams produced from stainless steel are one of the most recently developed ultralightweight materials. These foams have very low densities and high energy absorption capacities and are therefore expected to have widespread applications in the manufacture of ultralightweight structural components. The fabrication of load bearing structural components such as implants, and high temperature air or fluid filters, are potential application areas depending on the form of the cell structure of the foam. Closed cell metal foams are typically suitable for structural uses whereas open cell foams tend to be preferred for functional applications. Development of adequate joining technologies for these materials is an essential step for their widespread industrial utilisation. The present paper describes a brazing method that is capable of providing excellent joints between 316 stainless steel foams and a conventional 316 stainless steel bulk alloy. Having optimised the bonding conditions and using a Cu–Ti alloy as the filler metal, bonds between a foam and a bulk alloy were produced. No apparent plastic deformation of the metal foam occurred in the course of the 10 min length brazing process, and the resulting bonds had tensile strengths higher than that of the stainless steel foam.     

低热应变镁合金研究综述

镁和镁基合金是重要的轻量化金属材料,广泛应用于汽车、通讯、航空等领域。由于镁合金热膨胀系数较高,当应用于精密器件时易导致组装精密度降低、力学性能下降等问题。因此需要研发低热应变镁基材料,以满足此类应用的要求。本文对降低镁合金热膨胀系数的原理及方法进行综述,归纳比较了合金化、复合材料和特殊加工工艺等调整镁合金热膨胀系数的主要方法的原理,总结出高熔点元素合金化、高硬度颗粒掺杂、低热膨胀系数纤维掺杂以及热处理结合挤压加工方法等降低镁合金热膨胀系数的有效方法,并对未来该领域的研究趋势进行了展望。     

铝热法生产钛金属工艺的可行性研究

根据以金红石、铝粉、石灰为原料,利用铝热还原法生产钛合金的工艺启示,对该法生产金属钛和钛合金的工艺进行探析和热力学分析,证明了该方法生产金属钛的可行性.     

Extraction of titanium from different titania precursors by the FFC Cambridge process

Cheap titania precursors including titania dust, metatitanic acid (solid) and titanium-rich slag were tested as the feeding materials in the FFC Cambridge process (laboratory scale). Porous pellets (20 mm in diameter, 2.0–3.0 mm in thickness) of the precursor were successfully reduced to titanium metal or alloy by constant voltage electrolysis (2.9–3.1 V) in molten calcium chloride (900 °C). The reduction was independent of the initial crystal structure of the precursor. More importantly, some metallic impurities in the titanium-rich slag, such as aluminium and manganese, were found to be partly or completely removed after electrolysis. The current efficiency decreased with electrolysis time, typically from 40% in the first 5 h to 20% in 12 h for the 2 mm thick TiO₂ pellets. The energy consumption of electrolysis was about 33 kWh/kg Ti when the oxygen level in the produced metal was reduced to below 3000 ppm. Analyses of the electrolysis data and of the phases and compositions in partially reduced oxide pellets suggested strong dependence of the electro-reduction on mass (ion) transfer in the pellet after metallisation of the pellet's surface. An earlier proposed “double-melt electrolysis” was compared with the electrolysis data, focusing on the origin and influence of background current.     

Structure and properties of ultra-fine grain Cu–Cr–Zr alloy produced by equal-channel angular pressing

The structure, thermal stability and properties are investigated of a Cu–Cr–Zr alloy with ultra fine grains (UFG) of 160 nm diameter produced by severe plastic deformation through equal-channel angular pressing (ECAP). Special attention is paid to optimization of multi-functional thermal, electrical and mechanical properties of this alloy by aging after ECAP. Fatigue life and cyclic response under strain-controlled experiments are investigated aiming at clarification of mechanisms of plastic deformation and fracture in the precipitation hardened ECAP materials. It is shown that the precipitation strengthened UFG structure remains stable both under elevated temperatures as high as 500°C and under cyclic loading at room temperature. Substantial improvement of fatigue life is evidenced in comparison with conventional coarse-grain materials. The appearance of cyclic softening is noticed and its nature is discussed in terms of dislocation–particle interaction and possible dissolution of precipitates during fatigue.     

高温高强钨铼合金Gleeble热力模拟试验方法探讨

钨铼合金具有高熔点、高强度、高硬度、高再结晶温度等特点,作为结构材料广泛应用在特殊高温领域。针对采用Gleeble热力模拟试验机研究新型钨铼合金材料的高温热变形行为,存在热电偶焊接困难、钨铼合金强度高于碳化钨压头等问题,通过埋线法和耐高温无机胶固定热电偶,采用粉末热压烧结工艺制备碳化锆颗粒增强钨基复合材料作为高温高强压头进行解决,获得了钨铼合金在1 500 ℃、应变速率1s-1时压缩真应力 真应变曲线。该方法可用于测量钨铼合金真实高温强度,为钨铼合金工业生产过程中的热变形工艺参数确定提供准确数据。     

液相沉淀-热还原纳米Fe包覆Mo粉末微结构特征

采用液相沉淀-热还原法制备纳米Fe包覆Mo合金粉末,研究还原过程中的晶粒组织及微结构并进行分析.结果表明:还原过程中,粉末晶粒平均晶粒尺寸随还原温度的升高而变小,微观应变在还原温度为600 ℃时最高,Mo晶粒先于Fe晶粒还原并长大至1 μm左右,Fe晶粒粒径最终保持为1.8 nm,并形成20 nm左右的薄层,沉积在Mo颗粒表面.     

镁合金微弧氧化工艺参数研究

镁合金是目前最轻的金属,它可以部分替代一些钢铁材料来实现材料的轻量化。而且镁合金具有比强度、比刚度较高,减震性、减噪性、加工性较好等优点,市场对它的需求量也越来越大。但是镁合金的电位很低,易与其他金属发生电偶腐蚀,利用微弧氧化可在镁合金表面制得一层综合性能较好、类似陶瓷层的一种膜层,可大大提高镁合金的耐蚀性、耐磨性及耐高温性,因此微弧氧化技术在镁合金表面处理上得到了较快发展。对此,首先介绍了微弧氧化机理的研究现状,总结了微弧氧化过程的几个主要阶段及其主要作用;其次,重点概述了影响镁合金微弧氧化陶瓷膜制备工艺的主要因素,特别是电参数、电解液及氧化时间等对膜层结构、形貌及性能的影响;最后提出目前镁合金微弧氧化工艺存在的几个主要问题,并对其解决办法及应用前景进行了展望。     

冷喷涂辅助原位合成CuFeCrAlNiTi高熵合金涂层的组织性能研究

目的 为了提升普通金属材料的表面性能,提出了一种在普通金属材料表面制备性能较好的CuFeCrAlNiTi高熵合金涂层的技术工艺.方法 采用Cu、Fe、Cr、Al、Ni、Ti六种金属单质粉末为原料,经过2 h机械混合后,使用低压冷喷涂技术在45#钢基体上制备混合金属涂层,再经感应重熔技术将混合金属涂层原位合成为CuFeC...     

The study of electroless Ni-W-P alloy plating on glass fibers

Ni-W-P coatings were deposited on the surface of glass fibers by the electroless plating process. The bath was very stable through the palladium salt test. There was no phenomenon of peeling and blistering on the surface of the Ni-W-P alloy glass fibers in the thermal shock test. It showed that the deposit had high impact strength and good adhesion. The morphology of the coatings was observed by scanning electron microscope （SEM）. The elements and their contents were tested and analyzed by energy dispersion spectrometer （EDS）. The tungsten content reached up to 12.1 wt.%. The effects of the concentrations of NiSO4, Na2WO4, and NaH2PO2.H20 on the conductivity of the coatings were studied. The resistivity of the Ni-W-P alloy glass fibers reached 7.39 × 10^-3 Ωcm. The alloy coatings on glass fibers were analyzed by XRD. The results indicated that the deposit had an amorphous structure and good heat stability. The suitable work temperature range was lower than 190℃. Finally, the electromagnetic parameters of the Ni-W-P alloy glass fibers were tested and analyzed primarily. The magnetic loss reached 0.04023 and the dielectric loss reached -5.80239. The plated alloy is a kind of soft magnetic material.     

溶胶-凝胶法制备PZT纳米晶反应机理

以硝酸氧锆、钛酸四丁酯、醋酸铅为原料，乙二醇为溶剂，用溶胶—凝胶技术制备了钙铁矿型的锆钛酸铅(PZT)纳米晶。实验中发现前驱物间的聚合反应使硝酸氧锆能很好地溶于乙二醇。通过对原料、不同温度下的溶胶、干凝胶、PZT粉末的红外光谱分析，给出了溶胶、凝胶形成的机理，进一步证实溶胶—凝胶过程中通过前驱物的水解、缩聚反应形成金属元素与乙二醇相配位的链状或网状聚合物。原料中所含的NO3^—离子反应后形成的硝酸酯被包裹在溶胶和凝胶的聚合物网络中，CH3COO^—离子反应后生成醋酸酯并通过两个O与聚合物网络中的金属元素配位。     

机床复合结构热态特性的研究

机床热变形是影响机床精度的重要因素,占总制造误差的40％～70％,因此机床热变形控制技术成为当前的研究热点.添加相变材料的高孔隙率泡沫金属复合结构不仅能有效地减轻结构的质量,并具有良好的热特性.它利用相变材料的潜热特性,即物质在相变过程中吸收或释放一定的相变潜热而使温度保持不变.对复合结构热态特性进行仿真分析,结果表明:泡沫金属复合结构在受热情况下,在一定的时间范围内可保持在恒温状态不发生变化.这种热态特性对机床构件的制造具有重要意义,有利于减小机床的热变形,提高加工精度.