Crystal defects formed in electroformed nickel liners of shaped charges

Two types of electroformed nickel liners of shaped charges were prepared by electroforming technique. X-ray diffraction （XRD）, transmission electron microscopy （TEM）, electron backscattering diffraction （EBSD） technique and high resolution electron microscopy （HREM） have been employed to investigate the crystal defects formed in electroformed nickel liners of shaped charges. The result shows that （100） fiber texture which is parallel to the grown direction exists in the electroformed nickel prepared by using direct current electroforming without any additives, and （111） fiber texture exists in the electroformed nickel prepared by using direct current electroforming with additives. The deposits prepared by using direct current electroforming possess columnar grain with an average grain size of 30 μm in width and 170 μm in length. The deposits prepared with additives are composed of a colony structures with grain size of about 29 nm, and a lot of crystal defects such as twins, antiphase boundaries and stacking faults have been observed in the electroformed nickel.

Deformation behavior of explosive detonation in electroformed nickel liner of shaped charge with nano-sized grains

Nickel liner of shaped charge with nano-sized grains was prepared by electroforming technique and the ultra-highstrain-rate deformation was performed by explosive detonation.The as-electroformed and post-deformed microstructures of electroformed nickel liner of shaped charge were observed by optical metallography(OM),scanning electron microscopy(SEM) and transmission electron microscopy(TEM) and the orientation distribution of the grains was analyzed by electron backscattering pattern(EBSP) technique.Both melting phenomenon in the jet fragment and recovery and recrystallization in the slug after ultra-high-strain-rate deformation were observed.The research evidence shows that dynamic recovery and recrystallization play an important role in ultra-high-strain-rate deformation for electroformed nickel liner of shaped charge with nano-sized grain.

Microstructural evolution in electroformed nickel shaped-charge liners with nano-sized grains undergone deformation at ultrahigh strain rate

Nickel shaped-charge liners with nano-sized grains were prepared by the electroforming technique, and the deformation at ultrahigh strain rate was performed by explosive detonation. The as-formed and post-deformed microstructures of electroformed nickel shaped-charge liners with nano-sized grains were observed by means of transmission electron microscopy, and the orientation distribution of the grains was analyzed by the electron backscattering pattern （EBSP） technique. The melting phenomenon in the jet fragment and the recovery and recrystallization in the slug after plastic deformation at ultrahigh-strain rate were observed in the ultrafine-grained nickel shaped-charge liners. The research evidence shows that dynamic recovery and recrystallization play an important role in plastic deformation at ultrahigh strain rate.

Abrasive-assisted Nickel Electroforming Process with Moving Cathode

In traditional electroforming process for revolving parts with complex profiles, the drawbacks on surface of deposits, such as pinholes and nodules, will lead to varying physical and mechanical properties on different parts of electroformed components. To solve the problem, compositely moving cathode is employed in abrasive-assisted electroforming of revolving parts with complicated profiles. The cathode translates and rotates simultaneously to achieve uniform friction effect on deposits without drawbacks. The influences of current density and transla- tion speed on the microstructure and properties of the electroformed nickel layers are investigated. It is found that abrasive-assisted electroforming with compound cathode motion can effectively remove the pinholes and nodules, positively affect the crystal nucleation, and refine the grains of layer. The increase of current density will lead to coarse microstructure and lower micro hardness, from 325 HV down to 189 HV. While, faster translational linear speed produces better surface quality and higher micro hardness, from 236 HV up to 283 HV. The weld-ability of the electroformed layers are also studied through the metallurgical analysis of welded joints between nickel layer and 304 stainless steel. The electrodeposited nickel layer shows fine performance in welding. The novel compound motion of cathode promotes the mechanical properties and refines the microstructure of deposited layer.

Improvement of thickness deposition uniformity in nickel electroforming for micro mold inserts

Thickness deposition is a crucial issue on the application of electroformed micro mold inserts. Edge concentration effect is the main source of the non-uniformity. The techniques of adopting a non-conducting shield, a secondary electrode and a movable cathode were explored to improve the thickness deposition uniformity during the nickel electroforming process. Regarding these techniques, a micro electroforming system with a movable cathode was particularly developed. The thickness variation of a 16 mm×16 mm electroformed sample decreased respectively from 150% to 35%, 12% and 18% by these three techniques. Combining these validated methods, anickelmold insert for microlens array was electroformed with satisfactory mechanical properties and high replication precision. It could be applied to the following injection molding process.

Pulse electroforming of nickel under perturbation of hard particles

Nickel deposits were prepared by pulse electroforming, in which an aluminium alloy cylinder mandrel rotated in hard particles filling between the electrodes. The microstructure and properties of the deposits were studied by contrasting with electroforming using direct current. The results show that the surface of the deposits obtained by pulse electroforming displays more obvious abrasion marks and (200) preferred orientation to that electroformed using direct current at the same average current density. Besides, the deposits represent higher microhardness and better high-temperature corrosion resistance. It is also found that the orientation index of plane (200) and microhardness significantly increase with the reduction of duty cycle of pulse current. During pulse electroforming, the longer off-time and higher peak current density are helpful to strengthening the hard particles’ polishing effect on the surface of deposits and perturbing effect on crystal nucleation of atoms.

Effects of process parameters on mechanical properties of abrasive-assisted electroformed nickel

A cathode mandrel with translational and rotational motion, which was supposed to obtain uniform friction effect on surface, was employed in abrasive-assisted electroforming for revolving parts with complex profile. The effects of current density, translational speed and rotational speed on the deposit properties were studied by orthogonal test. The tensile strength, elongation and micro hardness value were measured to find out how the factors affected the properties. The optimized results show that changes of current density affect the tensile strength of nickel layer most, while translational speed has the most remarkable influences on both elongation and micro hardness. The low rotational speed affects the properties least. In this experiment, a smooth nickel layer with tensile strength 581 MPa, elongation 17% and micro hardness 248HV is obtained by the orthogonal test. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.

Microstructure and properties of electroformed nickel under different waveform conditions

In order to prepare electroformed nickel with excellent properties,the effect of different waveforms on microstructure and mechanical properties was investigated by optical microscopy(OM),X-ray diffraction(XRD) and tensile test,respectively.The results show that the samples are composed of micron columnar grains with high-density nanoscale coherent twin boundaries which are parallel to the growth plane.The tensile strength and elongation display opposite tendency with the increase in current density when direct current(DC) electroforming was applied.However,under the condition of pulse current(unidirectional,bidirectional) electroforming,the change regulation of tensile strength and elongation is close while cathode(peak,positive peak) current density increases.XRD results show that electroformed nickel layers with high purity are all fcc crystal configuration under different conditions of the current waveform.The nickel layers formed under bidirectional pulse current behave superior global performance with tensile strength of 692.0 MPa and elongation of 27.6 %.

硫酸盐电铸镍内应力的影响因素

研究了NiSO4·6H2O质量浓度、NiCl2·6H2O质量浓度、温度和阴极电流密度等工艺参数对硫酸盐电铸镍层内应力的影响。通过铜箔阴极弯曲法半定量地测定了镍铸层的内应力,采用扫描电镜和X射线衍射表征了镀层在不同应力状态下的表面形貌和微观结构。结果表明,当NiSO4·6H2O质量浓度为100～150g/L时,其变化对内应力影响较大;镀液中氯离子浓度的增加会增大镀层内应力;低温和大电流密度条件下获得的镀层具有大的拉应力,高温小电流则有利于降低镀层的拉应力。

硬质粒子摩擦法电铸新技术的研究

提出一种新型的硬质粒子摩擦法电铸技术,从理论上深入探讨了硬质粒子摩擦法电铸技术的沉积机理,并通过金属镍的电铸试验加以验证。理论分析和试验结果表明:硬质粒子摩擦法电铸技术在阴阳极之间引入硬质粒子,并通过电铸芯模的旋转,带动硬质粒子运动,使其不断摩擦、撞击阴极表面,能有效地去除沉积层表面的吸附气泡和积瘤,获得表面平整光亮的电铸层;通过减薄扩散层和扰动结晶过程,能细化晶粒,提高电铸速度。研究结果显示,硬质粒子摩擦法电铸技术在回转体类薄壁零件的电铸成形中有实用价值。

添加剂和电流密度对镍钴合金电铸层组织结构的影响

研究了添加剂、电流密度对镍钴合金电铸层应力和钴含量的影响。采用SEM、能谱仪和X射线衍射分析了添加剂和电流密度对铸层形貌及微观结构的影响。结果表明:添加剂TN2能够使铸层产生压应力;TN3能够使铸层产生张应力,TN3与TN2配合使用,能够使铸层应力达到平衡值零。电流密度增加时,当电流密度小于6A/dm2时,铸层应力随之增加;当电流密度大于6A/dm2时,铸层应力随之减小。添加剂对铸层钴含量影响不明显而电流密度对铸层钴含量的影响较明显;TN2,TN3的加入能够使铸层更平滑、晶粒细致紧密。添加剂TN2对衍射峰(200)影响较大,对晶面具有一定的选择性;添加剂TN3对晶面具有较强的选择性,易在(200)面吸附,抑制其生长,此时晶体的生长方向主要为[100]。随着电流密度的增大,衍射峰出现宽化的趋势。

溶液组分对电铸镍组织和力学性能的影响

在氨基磺酸盐溶液体系中电铸获得综合性能优异的铸镍层。利用金相显微镜、薄片阴极弯曲法和万能拉伸试验机评价测试溶液组分氨基磺酸镍和氯化镍对铸镍层的微观组织结构、内应力和力学性能的影响。结果表明:溶液经净化处理后,随着体系中氨基磺酸镍含量的逐渐增大,铸镍层的柱状组织越来越粗大,内应力和抗拉强度逐渐减小,而相应的伸长率则呈逐渐增大的趋势;随着体系中氯化镍含量的不断增大,铸镍层的柱状组织先逐渐粗化后再逐渐细化,内应力逐渐增大,抗拉强度先降低后升高,而相应的伸长率逐渐减小;当体系中氨基磺酸镍为300g/L、氯化镍为3g/L时,铸镍层的综合性能优异,此时铸镍层的内应力为60.7MPa,抗拉强度为811.7MPa,伸长率为23.5%。

超细晶粒镍药型罩的精密电铸试验研究

针对新型破甲聚能试验装置,分析了其核心部件药型罩的电铸过程中的电场分布。采取超窄脉宽电源和阴极旋转的方式,像形阳极、阴极电场局部屏蔽和去泡等辅助工艺措施,制备出高纯度、超细晶粒电铸镍药型罩。采用X射线等现代检测方法对电铸药型罩进行了检测,结果表明,药型罩含镍量不小于99.9%,电铸层晶粒尺寸小于100nm,且组织致密。晶体以细小的等轴-柱状晶方式生长,并存在明显的择优生长取向。电铸镍药型罩头部速度超过10km/s,射流的凝聚性和均匀性非常好,为提高破甲侵彻性能提供了保证。

电铸镍钴合金中内应力的影响因素

讨论了硫酸盐体系中影响镍钴合金电铸层内应力的因素。结果表明，内应力随钴离子质量浓度的增加而升高；随电流密度的增大先升高后降低，在6A／dm^2附近时应力最大；随温度的升高而降低；pH在3．0～4．5时应力较小。加入0．2～0．5g／L添加剂可有效消除内应力。

退火处理对电铸镍药型罩组织与性能的影响

通过对退火处理前后的电铸镍药型罩进行硬度测定、组织观察、晶体织构分析、残余应力测定,探讨退火热处理对电铸镍药型罩组织和性能的影响规律。研究结果表明,热处理后镍药型罩的硬度随着退火温度的升高而降低,高温退火时硬度急剧下降。在450℃以下退火热处理时,电铸镍药型罩的晶粒大小基本保持不变,超过550℃时发生再结晶,晶粒明显长大。随着退火温度的提高,晶粒的晶体取向发生改变。利用电子背散射衍射技术(EBSD)进行的分析结果表明,原始的镍药型罩在电沉积生长方向存在〈100〉丝织构,再结晶发生后丝织构消失。电铸镍药型罩内存在的残余应力为压应力,经退火处理后转变为拉应力。

氨基磺酸盐电铸镍药型罩的制备与微观组织

采用直流电铸法在氨基磺酸盐铸液中电铸制备镍药型罩,利用光学显微镜(OM)、X射线衍射仪(XRD)和背散射电子衍射(EBSD)技术对其组织结构进行观察和分析。研究结果表明:所制备药型罩表面质量良好,由于电铸过程中添加剂的不断消耗,从药型罩的内表面到外表面存在微观组织的不均匀性,晶粒沿平行于罩壁的法线方向呈柱状生长,在罩壁的法线方向存在<100>丝织构。

氨基磺酸盐溶液中电铸镍的微观组织及其夹杂物

采用直流电铸法在氨基磺酸盐铸液中电铸制备镍药型罩,利用光学显微镜(OM)、X射线衍射仪(XRD)和透射电子显微镜(TEM)等分析技术对其组织结构进行观察和分析,结果表明,所制备药型罩表面质量良好,铸层晶粒沿罩的壁厚方向呈柱状生长,在铸层的法线方向存在〈111〉丝织构。铸层镍的纯度不小于99.96%,含硫量为0.0056%。铸层内部存在镍的硫化物夹杂和大量位错。

超声辅助电铸钨丝–镍复合层的微观结构和抗拉强度

在钨丝–镍的复合电铸过程中施加超声辅助,以改善复合电铸层的组织结构,提高其抗拉强度。电铸液组成和工艺条件为:氨基磺酸镍400 g/L,氯化镍15 g/L,硼酸30 g/L,p H=4.5,温度43°C,电流密度4 A/dm^2,超声波频率100 k Hz,超声波功率120 W。研究了超声波辅助对钨丝–镍复合电铸层表面形貌、断口形貌、结晶取向、晶粒尺寸等微观结构及其抗拉强度的影响。结果表明:超声空化伴随的微射流和冲击波能够有效避免复合电铸层表面孔隙的形成,显著细化晶粒,减少内部空洞。超声波的应用改变了镍晶体的生长方式,显著提高了(200)面的择优程度。超声条件下获得的钨丝–镍复合电铸层具有更高的抗拉强度。当钨丝体积分数为50%时,超声辅助下所得复合电铸层的抗拉强度为1 502 MPa,比无超声条件下的复合电铸层高13.8%。

复合电铸制备Ni-石墨复合材料工艺及其沉积机理

采用复合电铸技术制备了Ni石墨自润滑复合材料,重点研究了工艺参数(微粒浓度、电流密度、电铸液流动速度及温度和pH值)对复合材料中石墨微粒含量的影响。结果表明,提高镀液中微粒浓度使复合材料中石墨含量增大,最后趋于稳定值。电流密度和镀液流动速度使石墨含量存在最大值,但是温度和pH值的增加却使之降低。复合电铸沉积机理Guglielmi模型只在低电流密度条件下适用,但不适用于高电流密度的条件。镀液中石墨微粒含量增大,复合材料的硬度和摩擦系数降低,磨损失重减小,但是石墨微粒30g/L时的磨损量增加。

钨丝镍复合电铸新技术

提出一种新的纤维金属复合电铸层——钨丝镍复合电铸层的电铸技术,研究脉冲电流、钨丝体积分数等对复合电铸层常温和中温拉伸性能的影响。结果表明:常温下,随着高强度钨丝的不断掺入,复合电铸层的拉伸强度不断提高,当钨丝的体积分数达到45%时,拉伸强度达到峰值1 650 MPa;脉冲电流的应用能够显著细化镍晶粒,降低复合电铸层内部孔隙率,获得的钨丝镍复合电铸层拉伸强度比使用普通直流的拉伸强度提高了30%左右;在200、400和600℃的中温条件下,钨丝镍复合电铸层依然具有很高的拉伸强度,但是随着温度的继续升高,拉伸强度迅速降低。