玻璃包覆Fe79-xCox Si8 B13非晶合金微丝的磁性能

实验以熔融纺丝法制备的玻璃包覆Fe79-xCoxSi8B13非晶合金微丝为对象,分析了微丝成分、尺寸以及玻璃包覆层去除对微丝静磁性能的影响。研究结果表明,玻璃包覆Fe79-xCoxSi8B13非晶合金微丝存在明显的磁各向异性,微丝轴向为易磁化方向;随着Co含量的增加,微丝的饱和磁化强度先增大后减小,Co含量为10%的Fe69Co10Si8B13非晶合金微丝饱和磁化强度最高,为1323emu·cm-3;对于玻璃包覆Fe69Co10Si8B13非晶合金微丝,当芯丝半径与玻璃包覆层厚度比值k约小于0.5时,其轴向磁滞回线为近矩形,表现出大巴克豪森效应;微丝的轴向剩磁比随k值的增大而减小,而微丝径向剩磁比保持很小,仅0.03左右;微丝的轴向和径向矫顽力均随比值k的增大而减小;当芯丝半径为10.9μm、玻璃包覆层厚度为9.7μm(k为1.12)时,去除包覆层后微丝的轴向矫顽力降低30%、径向矫顽力降低11%;而轴向剩磁比降低33%、径向剩磁比降低67%。     

小角磁转法测量玻璃包覆非晶丝的内应力

针对玻璃包覆非晶丝的内应力难以实验测量问题,提出了小角磁转法测量内应力的方法。内应力是在考虑其分布特点基础上通过测量磁弹性各向异性场而得出。采用该方法测量了不同退火温度下金属芯 直 径 为46.5μm,玻 璃 皮 厚 度 为8.7μm的Fe45Co20Ni10Si9B16玻璃包覆非晶丝的内应力。结果表明,淬态下去除玻璃皮前的内应力为385MPa;460℃退火后去除玻璃皮前的内应力降低至120MPa,去除玻璃皮后内应力降低至27MPa。该测量方法的精度能够达到±7%,对玻璃包覆非晶丝的基础研究和技术应用都具有重要意义。     

不同直径玻璃包覆非晶微丝的制备及其磁性能

采用熔融拉丝法制备了直径范围分别在6.1～28.0μm和14.0～35.2μm之间的玻璃包覆非晶Fe基和Co基合金微丝, 测试了不同合金直径和不同玻璃包覆层厚度的玻璃包覆合金微丝样品的静磁性能. 结果表明: 轴向矫顽力和轴向剩磁比随着微丝直径的增大而降低, 随着玻璃包覆层的增大而升高; 径向剩磁比的变化趋势则相反. 微丝合金直径和玻璃包覆层厚度改变, 静磁性能变化的主要原因是作用在合金芯上的内应力的变化, 导致了具有不同磁畴结构的合金内芯区和合金外壳区体积比的改变.     

Fe73.5Cu1Nb3Si13.5B9纳米晶合金在NaCl溶液中耐腐蚀性能研究

研究了Fe73.5Cu1Nb3Si13.5B9纳米晶合金在0.1mol/L的NaCl溶液中的耐腐蚀性能,及对其软磁性能的影响。实验结果表明,Fe73.5Cu1Nb3Si13.5B9纳米晶合金经0.1mol/L的NaCl溶液腐蚀后溶液中有橙色沉淀物产生,XRD测试表明铁基纳米晶合金腐蚀后仍保留非晶纳米晶双相结构;铁基纳米晶合金有效磁导率μe随腐蚀时间的增加而降低,腐蚀30d后在频率为50Hz、1、100kHz时其有效磁导率μe较腐蚀前分别下降35.9%、35.3%、27.6%,矫顽力Hc由腐蚀前的0.7097A/m增加到1.117A/m,增加了57.4%,磁滞损耗Pu由腐蚀前的1.819J/m3增加到2.994J/m3,增加了64.6%,腐蚀后铁基纳米晶合金软磁性能有所下降。     

强酸碱环境下玻璃包覆纯铜微丝的腐蚀行为

采用熔融纺丝法制备了玻璃包覆纯铜微丝,对微丝表面玻璃包覆层的去除进行了实验研究,评价了微丝在氢氟酸和熔融氢氧化钠中的腐蚀行为,分析了玻璃包覆纯铜微丝在强酸和强碱中的耐腐蚀性能,探讨了其腐蚀机理.研究表明:氢氟酸和熔融氢氧化钠都能用于微丝表面玻璃包覆层的去除,室温下氢氟酸去除厚度为10 μm的玻璃包覆层的时间大约为150 s,熔融氢氧化钠大约需要10 s;玻璃的成分和结构是影响玻璃包覆纯铜微丝耐腐蚀性能的重要因素.     

(Fe50Co50)73.5Cu1Nb3Si13.5B9合金的微观结构及软磁性能

研究了(Fe50Co50)73.5Cu1Nb3Si13.5B9合金晶化过程中的微观结构及形成纳米晶后的合金软磁性能,发现在FINEMET合金基础上,用Co置换1/2含量Fe形成的(Fe50Co50)73.5Cu1Nb3Si13.5B9非晶合金具有相对较高居里温度Tc≈450℃,460℃退火处理后(Fe50Co50)73.5Cu1Nb3Si13.5B9合金形成均匀纳米晶组织,晶粒度约为20nm.     

Fe61Co10Zr5W4B20块体非晶合金的形成及其力学性能

采用铜模吸铸法获得直径为2 mm的Fe61Co10Zr5W4B20块体非晶合金.采用X射线衍射、扫描电镜、示差扫描量热仪、微显硬度及压缩实验等研究了非晶合金的结构、热稳定性、显微硬度与压缩性能.结果表明:Mo的引入不利于非晶合金的形成;Fe61Co10Zr5W4B20块体非晶合金表现为二级晶化,玻璃转变温度为561.1℃,晶化起始温度为619.0℃,第一晶化峰值温度为632.6℃,第二晶化峰值温度为747.0℃,过冷液相区为57.9℃;该非晶合金的显微硬度为1207HV0.2,抗压强度σbc为1707.6 MPa.     

玻璃包覆铁基合金微丝的微结构与吸波性能

采用熔融纺丝工艺制备了玻璃包覆Fe基非晶合金微丝,通过X射线衍射分析研究了工艺条件对其微结构的影响,采用扫描电子显微镜分析了拉丝速度对微丝直径、玻璃包覆层厚度等结构参数和形貌的影响,利用微波矢量分析仪测量了2～18GHz的复磁导率和复介电常数,计算模拟了1mm厚度单层吸波材料的吸波性能.结果表明,通过冷却水急冷淬火可以获得非晶态结构,氩气保护可以防止合金氧化;拉丝速度提高有利于减小微丝直径,但玻璃包覆层的体积含量也随之增加;由该玻璃包覆Fe基非晶合金微丝设计的薄层吸波材料,在3～18GHz的宽频段内可以获得＜-2.5dB的微波吸收性能.     

玻璃包裹Fe基纳米晶丝的高频巨磁阻抗效应

采用高频感应加热熔融拉引法制备玻璃包裹Fe73.0Cu1.0Nb1.5V2.0Si13.5B9.0纳米晶丝,细丝直径D约为3～20μm,玻璃层厚度d在1～2μm之间,其中玻璃层厚度占细丝总直径较小.研究结果发现,玻璃包裹Fe73.0Cu1.0Nb1.5V2.0Si13.5B9.0纳米晶细丝具有良好的高频巨磁阻抗效应,细丝磁阻抗的变化主要由电阻部分的变化决定,同时出现最大磁阻抗变化时对应的外磁场值Hm随频率的增加向高场方向移动.系统研究了不同条件细丝在趋肤效应开始明显时的起始频率f0变化情况,讨论了影响f0的各种可能因素.     

退火对玻璃包覆Fe_(69)Co_(10)Si_8B_(13)非晶微丝磁性能及力学性能的影响

研究了退火对玻璃包覆Fe69Co10Si8B13非晶合金微丝磁性能和力学性能的影响。结果表明,退火温度为450℃时,矫顽力和剩磁比最小,轴向和径向矫顽力分别为1.8Oe和8.5Oe,比退火前降低了31%和36%,轴向和径向剩磁比分别为0.031和0.012,比退火前降低了74%和63%。当退火温度低于450℃时,芯丝抗拉强度基本保持不变,平均抗拉强度约2500MPa;当退火温度高于450℃时,芯丝抗拉强度迅速降低。未退火及退火温度低于450℃退火时,合金芯丝断口存在少量的脉状花样,且脉状花样及花样交叉的数量越多,所对应的芯丝抗拉强度越高;经500℃以上退火后,放射状撕裂区占芯丝断口大部分面积,芯丝表现出更大的脆性。在450℃20min条件下退火,微丝具有较低的矫顽力和较高的强度,综合性能优良。     

A study of the mechanical and fatigue properties of metallic microwires

There is an increasing necessity to record the deformation characteristics of microelements containing freestanding bond wires. The data required are either mechanical or thermal such as Young's moduli, stress–strain values, fatigue‐ and thermal‐strain data, but the nominal strength of a structure changes by scaling its size. Due to this size effect, material data cannot be taken from macrospecimens, thus special testing procedures were introduced. Laser optical sensors based on the speckle correlation technique were applied to determine non‐contacting strain values with high strain resolution. For the mechanical properties tensile tests were used. A special ultrasonic resonance fatigue system is described for testing freestanding microwires. In this study the stress–strain and fatigue response of microwires of Cu with a purity of 99.99+% with diameters between 10 and 125 μm with a typical bamboo structure have been investigated. A size dependence of the yield strength which increased with decreasing diameter was observed, while the fracture elongation showed contrary behaviour. Fatigue life also decreased with reduced diameters. An explanation is presented based on formed oxide layers, strengthening effects by dislocation pile‐ups and a pronounced localization of formed slip steps acting as notches being most dominant in the very thin microwires.     

Effect of processing parameters on static strength of dissimilar friction stir spot welds between different aluminium alloys

The effect of processing parameters on static strength and fracture mechanisms of dissimilar friction stir spot welds between different aluminium alloys was studied. Tensile shear strength increased with decreasing tool rotational speed and increasing tool holding time, while cross tension strength decreased with increasing both parameters. Two fracture modes were observed: nugget shear fracture and mixed mode fracture under tensile shear loading, and debonding and pull‐out of the nugget under cross tension loading. Based on experimental observation, the dependence of static strength on processing parameters and the occurrence of different fracture modes were discussed.     

Modelling the quasi-static behaviour of bituminous material using a cohesive zone model

This paper investigates the applicability of a cohesive zone model for simulating the performance of bituminous material subjected to quasi-static loading. The Dugdale traction law was implemented within a finite volume code in order to simulate the binder course mortar material response when subjected to indirect tensile loading. A uniaxial tensile test and a three-point bend test were employed to determine initial stress-strain curves at different test rates and the cohesive zone parameters (specifically, fracture energy and cohesive strength). Numerical results agree well with the experimental data up to the peak load and onset of fracture, demonstrating the value of the cohesive zone modelling technique in successfully predicting fracture initiation and maximum material strength.     

Evaluation of material degradation of 1Cr-1Mo-0.25V steel by ball indentation and resistivity

In this study, test materials with several different degradation levels were prepared by isothermal aging heat treatment at 630 °C up to 1820 h. Tensile and fracture tests were performed and those were compared with BI tests and DC potential drop method. These results show that normalized Brinell hardness agrees well with normalized tensile strength at the viewpoint of material degradation and the tensile strength and fracture toughness of degraded material can be determined by Brinell hardness or resistivity.     

拉伸速度和制样方式对聚苯乙烯和聚丙烯拉伸性能的影响

研究了拉伸速度及制样方式对聚苯乙烯(PP)和聚丙烯(PS)材料的拉伸强度和断后伸长率的影响。结果表明:随着拉伸速度的增大,两种材料的拉伸强度均有所增加,而断后伸长率却呈现出不同的变化;PS注塑成型试样的拉伸强度和断后伸长率都明显高于压制成型试样,PP注塑成型试样的断后伸长率比压制成型试样的增加了69%,而拉伸强度几乎没有改变。     

Effect of corrosion on mechanical behaviors of Mg-Zn-Zr alloy in simulated body fluid

The main purpose of this paper is to investigate the effect of corrosion on mechanical behaviors of the Mg-Zn-Zr alloy immersed in simulated body fluid （SBF） with different immersion times. The corrosion behavior of the materials in SBF was determined by immersion tests. The surfaces of the corroded alloys were examined by SEM. The tensile samples of the extruded Mg-2Zn-0.8Zr magnesium alloy were immersed in the SBF for 0, 4, 7, 10, 14, 21 and 28 d. The tensile mechanical behaviors of test samples were performed on an electronic tensile testing machine. SEM was used to observe the fracture morphology. It was found that with extension of the immersion time, the ultimate tensile strength （UTS）, yield strength （YS） and elongation （EL） of the Mg-2Zn-0.8Zr samples decreased rapidly at first and then decreased slowly. The main fracture mechanism of the alloy transformed from ductile fracture to cleavage fracture with the increasing immersion times, which can be attributed to stress concentration and embrittlement caused by pit corrosion.     

Enhanced tensile ductility of tungsten microwires via high-density dislocations and reduced grain boundaries

Despite being strong with many outstanding physical properties,tungsten is inherently brittle at room temperature,restricting its structural and functional applications at small scales.Here,a facile strategy has been adopted,to introduce high-density dislocations while reducing grain boundaries,through elec-tron backscatter diffraction (EBSD)-guided microfabrication of cold-drawn bulk tungsten wires.The de-signed tungsten microwire attains an ultralarge uniform tensile elongation of ～10.6％,while retains a high yield strength of ～2.4 GPa.in situ TEM tensile testing reveals that the large uniform elongation of tung-sten microwires originates from the motion of pre-existing high-density dislocations,while the subse-quent ductile fracture is attributed to crack-tip plasticity and the inhibition of grain boundary cracking.This work demonstrates the application potential of tungsten microcomponents with superior ductility and workability for micro/nanoscale mechanical,electronic,and energy systems.     

工艺参数对7075铝合金板材时效成形性的影响

为评价7075铝合金板材的可时效成形性并掌握最佳的时效成形工艺参数,基于机械加载时效成形试验工装,开展了时效温度和时间对7075铝合金板材时效成形后构件力学性能和物理性能影响的试验研究.结果表明:7075铝合金板材的时效成形性与工艺参数密切相关,随着时效温度和时间的增大,板材的电导率呈升高趋势,而其拉伸性能则呈降低趋势;且合金的拉伸断裂方式与时效状态有关,过时效初期以沿晶韧窝和穿晶韧窝混合型断裂为主,随着过时效进行主要为韧窝断裂.综合考虑构件时效成形后拉伸性能和电导率等情况,合金最佳时效温度为180℃,且保温时间不宜长于16 h.     

基体合金对连续M40石墨纤维/Al复合材料纤维损伤及断裂机制的影响

选用M40石墨纤维为增强体,采用真空气压浸渗法制备了纤维体积分数为40%,基体合金分别为ZL102、ZL114A、ZL205A及ZL301合金的连续M40/Al复合材料,并用NaOH溶液萃取出M40纤维,研究了基体合金对连续M40/Al复合材料纤维损伤和断裂机制的影响。结果表明:不同的基体合金对M40纤维造成的损伤差异较大,从M40/ZL301复合材料中萃取的纤维拉伸强度最高,其拉伸强度为1 686 MPa,约为纤维原丝拉伸强度的38.3%;而从M40/ZL102复合材料中萃取的纤维拉伸强度最低,其拉伸强度仅为687 MPa,且纤维表面粗糙程度不一。不同M40/Al复合材料的断裂机制存在明显差别,M40/ZL102和M40/ZL114A复合材料断裂时无纤维拔出及界面脱粘,裂纹横向穿过纤维导致复合材料在低应力下失效;M40/ZL205A复合材料则表现为少量纤维拔出,界面轻微脱粘;同时,M40/ZL301复合材料表现为大量纤维拔出,裂纹沿界面纵向扩展,界面脱粘明显,纤维充分发挥其承载作用,复合材料的拉伸强度最高,达到了670.2 MPa。