电塑性加工研究进展

论述了电塑性效应提高材料加工性能的原理,综述了电塑性在传统塑性加工工艺中应用的研究新进展。对电塑性在其他加工工艺中的应用也进行了介绍,展望了电塑性加工的发展趋势和应用前景。     

冷拔钢管的残余应力测试与结果分析

分析盲孔法测量冷拔钢管表面残余应力的测试结果,得出冷拔钢管各工序表面残余应力的分布规律,并将理论分析结果与测试结果进行对比;根据应力分布测试结果,优化冷拔加工工艺;提出消除冷拔钢管有害残余应力的方法与措施。分析认为:等径冷拔工艺生产的冷拔钢管,其表面残余应力很小,均为压应力,材料的综合性能良好;两道次冷拔中间增加一次退火,对消除成品表面残余应力没有明显效果;总变形量不变的情况下,增大第一道次冷拔变形量,减小第二道次冷拔变形量,可得到表面残余应力更小的冷拔钢管。     

超声波拉丝新工艺

超声波应用于金属塑性加工是近十几年来开发的新技术。超声波应用于拉丝能增加金属塑性,改善金属丝材性能和表面光洁度,节省能源。超声波拉丝新工艺也适宜于各种难加工材料(如高温合金、超导材料、高弹性材料)的拉     

电(致)塑性效应在材料加工中的应用研究进展

材料在电场或外加电流的刺激下,各项性能会发生改变,塑性提高,变形抗力下降,即电塑性效应。近年来,在材料加工的各领域已经开始广泛将这一效应用于材料的改性研究中,取得了显著地成果。基于此,综合评述了电(致)塑性效应微观机理及影响因素的研究现状,分析了电(致)塑性效应中电子风力及漂移电子对材料内部位错的影响,讨论了电(致)塑性效应对材料显微组织及力学性能的影响,并对电(致)塑性在材料加工中的应用研究进展进行综述。同时对电(致)塑性效应在材料加工方面的应用做出了展望,为电(致)塑性效应在材料加工中的广泛应用提供参考。     

电火花加工NdFeB材料的表面性能

为在NdFeB材料成型加工的同时实现其表面改性,研究了电火花加工对钕铁硼材料的影响。利用电火花成型加工技术,在不同电参数下,用紫铜电极对钕铁硼材料在绝缘介质中进行负极性加工。用扫描电子显微镜(SEM)、X射线衍射仪(XRD)等分析了材料的表面层成分、表面形貌及组织结构。通过显微硬度分析及盐雾试验,测试了材料表面硬度和耐蚀性能。结果显示:在大脉冲宽度24μs、小峰值电流5.6A下,电火花加工材料的表面质量较好。在其他参数相同的条件下,峰值电流从25.6A增大到50A,脉冲宽度从4.2μs增大到13μs时,时,硬度最大值均超过900HV0.3,比基体高出近300HV0.3。盐雾试验中加工前后材料开始出现斑点的时间差为20h,耐腐蚀性能明显发生变化。电火花加工后的钕铁硼材料表面组织中晶粒尺寸减小,并存在非晶合金相。表层非晶合金使钕铁硼材料的硬度及耐腐蚀性能得到明显地改善。     

电拔丝工艺及装置研究动态及展望

电塑性拔丝工艺是目前解决塑性差、难变形金属材料加工难题的一种重要途径,其原理是电致塑性效应。本文对电致塑性效应的研究进展进行了综述,从宏观性能和微观组织等方面,论述了电拔丝工艺对材料的影响;综述了电拔丝工艺及其装置的原理及研究现状,并总结了电拔丝装置的简要设计准则。指出了电致塑性效应及电拔丝工艺亟待解决的问题,展望了其在实际应用中的前景。     

高能电脉冲对淬火态GCr15钢切削性能的影响

在高频淬火态GCr15轴承钢切削过程中施加高能脉冲电流,研究了高能电脉冲对淬火态GCr15钢切削性能的影响。结果表明,在脉冲电流的作用下,主切削力、轴向表面粗糙度、表面硬度以及刀具磨损状况都显著降低。对高频淬火态GCr15轴承钢而言,脉冲电流的电致塑性效应与焦耳热效应能够促进位错运动,从而在较低温度与较短时间内达到回火效果,提高材料表面塑性变形能力,有效改善其切削加工性能。     

大块非晶合金超塑性变形的研究现状与发展

文章对国内外非晶合金超塑性基本性能的研究工作进行了介绍和评述。根据材料成形工艺的要求,提出了非晶合金超塑性成形研究的内容。介绍了非晶合金超塑性拉伸实验和压缩实验的研究进展,分析了温度和成形速率对变形的影响,介绍了粘度的影响因素,对这些研究内容和热点问题进行了评述。展望了非晶合金超塑性研究的发展趋势,提出应加强非晶合金超塑性流动过程的理论研究。     

高耐腐蚀Fe-(Cr,Ni)-Mo-P-C-B块体非晶合金

Fe-Mo-P-C-B铁基块体非晶合金具有高强度、高塑性和良好的软磁性,作为结构和功能材料具有较好的应用前景。本研究通过Cr、Ni合金化制备了耐腐蚀Fe-(Cr,Ni)-Mo-P-C-B块体非晶合金,其非晶形成临界直径达5mm。Cr、Ni合金化显著提高了Fe-Mo-P-C-B块体非晶合金在HCl、H2SO4、NaCl溶液中的耐腐蚀性能,使钝化电流密度降低、腐蚀速度降低、电化学反应电阻增大。     

利用金刚石线锯切割硅晶体的实验研究

本文综述了脆性材料的塑性转变理论、脆性材料塑性加工研究进展情况,进行了环形金刚石线锯丝切割硅晶体的实验.锯丝单方向连续运动,因而可以提高切割速度,锯丝运动速度为10 m/s和21 m/s两种.工件进给速度分别为8.4 mm/min,12.6 mm/min和20 mm/min等三种.用扫描电镜检测切割表面并与往复式线锯切割表面进行比较.实验结果及理论分析表明:锯丝上单个磨粒切削深度极小,切割表面平整、无崩碎现象,表面粗糙度值达1.4 μm～3 μm,接近粗磨加工后的表面.进给速度增大,表面粗糙度有所增大;切削速度提高,表面粗糙度降低不明显,这与理论分析不一致,其原因是工艺系统振动、冲击所致.锯丝磨损、磨料脱落是降低切割表面质量的另一原因.     

Magnetic properties of micro- and nanowires in the superhigh-frequency range

The skin-effect theory is presented using the example of an amorphous ferromagnetic material taking into account the ferromagnetic resonance. The theoretical dependence of the impedance of a microwire on its magnetic permeability is determined. The results allow analyzing experiments on studying the high-frequency properties of amorphous microwires.     

非晶玻璃包裹细丝的制备与铁磁共振性能的应用

非晶玻璃包裹细丝不仅具有电、磁、强度和塑性等方面的显著特点,而且具有突出的自然铁磁共振性能,作为吸波材料具有潜在的应用价值.阐述了玻璃包裹熔融纺丝法制备非晶玻璃包裹细丝的基本原理和实验参数,介绍了细丝产生铁磁共振性能的基本原理,及在吸波材料方面的应用.     

Magnetic and microwave properties of glass-coated amorphous ferromagnetic microwires

Glass-coated amorphous FeCuNbSiB microwires were prepared by Taylor-Ulitovsky technique. X-ray diffractometry and scanning electron microscopy were used to investigate the microstructure and morphology of the glass-coated microwires respectively. The vibrating sample magnetometer and vector network analyzer were used to study the magnetostatic and microwave properties of glass-coated microwires. The experimental results show that the effective anisotropy of an array of 150 microwires of 10 mm in length is large than that of one microwire of 10 mm in diameter and an array of 150 microwires of 1 mm in diameter. The natural ferromagnetic resonance takes place as the microwave magnetic component is perpendicular to the microwires axis, and the electric dipole resonance takes place as the microwire is long or the short microwire concentration is moderate. The natural ferromagnetic resonance shifts to higher frequency with the larger microwire concentration. The electric dipole resonance is governed by the microwires length and concentration. The glass-coated FeCuNbSiB microwires can be used to design EMI filters and microwave absorbing materials.     

Effect of a glass shell on the crystallization of Fe- and Co-based amorphous microwires

Crystallization of amorphous Fe_73.9B_13.2Si_10.9C₂ and Co_73.6B_11.2Si₁₃C₂ microwires in a glass isolation (shell) upon heating has been studied by X-ray diffraction. Crystallization of the core of an amorphous microwire starts at temperatures above 400°C. No noticeable effect of the glass shell on the crystallization of the Fe-based microwire was observed. The crystallization of the Co-based microwires with a glass shell begins at a lower temperature than the crystallization of those without a shell. There has been observed a difference in the effect of the glass shell on the crystallization of microwires of different chemical compositions.     

Design of multilayer microwires with controllable magnetic properties: Magnetostatic and magnetoelastic coupling

Novel two-magnetic-phase multilayer microwires with outstanding controllable behaviour are introduced. They are obtained by suitable combined processing techniques, such as the quenching and drawing method, sputtering and/or electroplating, and consist of a magnetic nucleus, intermediate non-magnetic layers and an outer magnetic layer. In this work, an ultrasoft CoFe-based amorphous nucleus and a magnetically harder crystalline CoNi outer layer are considered. The magnetostatic interaction between magnetic phases is proven to give rise to antiferromagnetic-like coupling, resulting in biasing of the magnetic behaviour of the soft nucleus. In addition, the effective magnetic anisotropy of the latter is tailored by the magnetoelastic coupling between the nucleus and the external layers through the stresses induced during the fabrication process and by their differential thermal expansion coefficients. This new family of microwires shows excellent magnetic properties which, being tailorable, make them ideal materials for novel or optimized elements in sensor devices.     

Relating residual stress and microstructure to mechanical and giant magneto-impedance properties in cold-drawn Co-based amorphous microwires

The effect of cold-drawing on the tensile property and giant magneto-impedance (GMI) effect of melt-extracted Co-based amorphous microwires was evaluated through detailed analyses of the distribution of residual stress and microstructural evolution. The tensile ductility and tensile strength increased gradually with cross-sectional area reduction ratio (R) until 51%, and decreased with further deformation. The microwire with R = 51% exhibits the highest tensile ductility of 1.09% and tensile strength of 4320 MPa. Structural and thermodynamic analyses reveal that it is the mechanical deformation rather than thermal activation that induces the precipitation of nanocrystals and arrests the quick extension of shear bands leading to the enhanced ductility. Interestingly, the GMI effect also attains the maximum value of 160% at 10 MHz when R = 51% (30% larger than that of the as-cast wires), before decreasing with further cold-drawing. Such an identical evolution trend of both tensile and GMI properties can be ascribed to two underlying mechanisms: the generation of longitudinal and circumferential residual stresses and the growth of deformation-induced nanocrystals during cold-drawing. The role of residual stress is established herein not only as a trigger to accelerate the amorphous-to-nanocrystalline phase transformation but also as a decisive contributor to the mechanical and GMI performance. The unique simultaneous improvement of both mechanical and GMI properties of cold-drawn Co-based microwires opens up new possibilities for a variety of engineering applications, such as high-performance magnetic, stress and biological sensors.     

Magnetic models of cast amorphous microwires

A theory of a magnetic domain model for glass-coated amorphous microwires is studied. The obtained theoretical results are confirmed by experiments. Cast glass-coated amorphous microwires with positive magnetostriction have a rectangle hysteresis loop, which is characterized by a coercive-force stable magnitude. The coercive-force magnitude and the fluctuations of this magnitude are of theoretical and practical interest. The theory of the relaxation mechanism of magnetic reversal is constructed. For the more precise comparison of the theory and the experiment, a series of experimental measurements is needed, which are also discussed in the paper.     

熔体过热水平对Cu36Zr48Ag8Al8块体非晶合金热稳定性和力学性能的影响

熔体过热度对Cu36Zr48Ag8Al8块体非晶合金的热稳定性和力学行为有显著影响。高的过热水平制备非晶合金的比热容大,初始缺陷密度小,热稳定性高。过热度越小,压缩塑性越小;抗压强度和维氏硬度随着过热度的减小先增加后下降。自由体积和残余应力共同影响不同吸铸电压制得非晶合金的力学性能     

The effect of mechanical stress on Ni63.8Mn11.1Ga25.1 microwire crystalline structure and properties

We studied structure and magnetic properties of Heusler alloy microwires. The dependence of the phase composition of the annealed microwires on the presence of glass coating has been found. The crystalline structure of the glass-coated samples is composed of two cubic crystalline phases of different density. The samples annealed without coating are in the single-phase state. The two-phase state is supposed to be caused by intrinsic stresses resulted from the action of opposite sign stresses in different microwire sections. The magnetic properties of the fabricated Heusler-type microwires differ from their bulk and thin film counterparts. Annealing of microwires considerably affect magnetic properties at room temperature. Unusual magnetic behavior is connected with two-phase structure of microwires.     

Experimental measurement of residual stresses in microwires

Methods of measurement of residual stresses in cast amorphous microwires are submitted. The obtained experimental results confirm the earlier given theoretical conclusions.