脉冲电沉积纳米晶Ni-Co合金镀层热稳定性的研究

采用X射线衍射(XRD)、能谱分析(EDS)等方法研究脉冲电沉积法制备的纳米晶Ni-Co合金镀层的组织结构和合金成分.测定不同退火温度下纳米晶Ni-Co合金镀层的显微硬度,并着重研究Ni-23.5%Co(质量分数)合金的热稳定性,结果表明:随着退火温度的升高,纳米晶Ni-Co合金在低温退火后显微硬度有所升高,在250℃时达到最高值,然后随退火温度的继续升高而降低.纳米晶Ni-23.5%Co合金镀层的晶粒尺寸逐渐增大,从原始晶粒尺寸13.5nm长大到300℃时的98.5nm,在升温速率为20K·min-1的DSC曲线中,Ni-23.5%Co合金在约300～350℃一直是低能放热,随后出现明显的放热峰,其峰值温度为372℃,放热焓为14.22J·g-1.通过测定不同升温速率条件下的DSC曲线峰值温度,由Kissinger方程求得纳米晶Ni-23.5%Co合金镀层的晶粒长大激活能为212.SkJ/mol.     

电沉积纳米晶镍的研究现状及展望

综述了电沉积法的特点和基本过程,电沉积纳米晶镍的制备工艺,电沉积纳米晶镍的织构和热稳定性,以及电沉积纳米晶镍的强度和硬度;展望了电沉积纳米晶镍的研究趋势.     

改性非晶和纳米晶FINEMET合金的显微硬度研究

本文研究了用元素W部分替代典型FINEMET合金中Nb和Fe的新型合金Fe73.3Cu1 Nb1 .5W1 .7Si1 3.5B9,在淬火态和不同退火温度及保温时间下 ,结合不同载荷大小和加载时间测试合金带芯部的显微硬度。随着纳米晶化的进行 ,自由体积缺陷含量和纳米晶晶界比例的变化会显著影响Fe73.3Cu1 Nb1 .5W1 .7Si1 3.5B9合金的显微硬度 ;合金在非晶态下有一定的压痕尺寸效应 ,而经过 4 5 0℃和 6 0 0℃退火 1h ,压痕尺寸效应消失 ;在 5 5 0℃退火温度下 ,在 0 .1kgf～ 0 .2kgf之间压痕尺寸效应不明显 ;合金的显微硬度变化趋势不符合超塑性波动公式。     

脉冲电沉积纳米晶镍沉积层的力学性能研究

为了提高镍沉积层的显微硬度和抗拉强度,采用传统的Watt镀液通过脉冲电沉积制得纳米镍沉积层.通过扫描电镜(SEM)、X射线衍射(XRD)方法分析了沉积层的表面形貌、织构和晶粒大小与脉冲参数的关系.分析表明,微观形貌为胞状结构,平均晶粒尺寸为10.3 nm;随着占空比减小,晶粒得以细化.研究了脉冲参数对纳米镍镀层显微硬度、抗拉强度的影响,最大显微硬度达到591 HV,最大拉伸强度达900MPa,分别为直流镍镀层的4.0和1.4倍;热处理试验表明,200℃热处理有利于提高镍镀层的显微硬度.     

热处理对化学沉积Ni-Fe-P合金磁性能的影响

采用差示扫描量热、X射线衍射和扫描电镜研究了化学沉积Ni-Fe-P合金的晶化行为和表面形貌.结果表明,镀态合金呈非晶结构,367.6℃下热处理出现亚稳态Ni5P2(P3)和Fe-Ni(Im3m),499.2℃下热处理进一步晶化为稳定的Ni3P(I-4)和FeNi3(Pm3m).镀层经过500℃热处理生成许多粒径为30～50nm的纳米颗粒,而经过600℃热处理后颗粒变大.研究了热处理对镀层显微硬度和磁性能的影响.发现该镀层在镀态时和经过200℃热处理后几乎没有磁性,随着退火处理温度的升高,镀层的显微硬度和磁性能不断提高;500℃达到最高,随后这些性能随着退火温度的升高而降低.     

化学沉积钴基纳米晶合金涂层工艺

化学沉积是制备纳米材料的一种良好方法,通过控制溶液组份和操作条件可以获得不同尺度的纳米晶.在化学沉积钴硼、钴磷合金纳米晶涂层制备工艺的基础上,制备了钴镍硼、钴镍磷纳米晶合金涂层,研究了三元纳米晶合金的沉积速率和显微组织结构.结果表明:当CCo2 /CNi2 =3:2时,pH值7.2,温度80℃,负载因子0.4 dm2/L,可以获得钴镍硼合金纳米晶.以纳米晶钴磷合金沉积液为基本配方,CCo2 /(CCo2 CNi2 )保持在0.1～0.5之间变化,可获得较好的纳米晶钴镍磷合金沉积层.     

添加Sc、Zr和退火对Al-Si合金铸态力学性能的影响

使用OM、TEM、SEM、显微硬度和室温拉伸等手段研究了Sc和Zr的复合添加对Al-5.5Si合金铸态的组织和性能的影响,以及在不同温度退火后其性能的变化规律。结果表明,Sc、Zr的添加使Al-5.5Si合金的硬度提高了33%、抗拉强度提高了38%、屈服强度提高了52%、延伸率基本上不变。在Al-5.5Si合金中复合添加Sc、Zr使α-Al的平均晶粒尺寸从203 μm减小到130 μm,在α-Al基体中析出大量的Al₃(Sc_1-xZr_x)纳米粒子(10~15 nm),并使共晶Si内的层错或微孪晶的密度显著提高。退火温度对铸态合金的性能有较大的影响：在较低温度(低于160℃)退火时合金的硬度呈上升趋势,而在较高温度(高于280℃)退火时合金的硬度呈显著下降趋势。这些结果与二次析出的纳米Si相密切相关。     

Fe_(78)B_(13)Si_9纳米晶合金中的 Hall-Petch 关系

采用晶化法由 Fe_(78)B_(13)Si_9非晶态合金条带制备纳米晶合金,测定了纳米晶合金的显微硬度。晶粒尺寸在纳米数量级时,Hall-Petch 关系仍然成立。FeBSi 纳米晶合金的硬度值约为相同成分的粗晶粒状态合金的2倍。位错作用机制仍为强度提高的主要因素。     

Er对汽车框架用铝合金组织与性能的影响

对比分析了不同退火温度下不含Er和含Er铝合金显微组织、显微硬度、拉伸力学性能和断口形貌的变化规律。结果表明,在相同退火温度下,含Er铝合金的显微硬度都要高于不含Er铝合金;相同的退火温度下,含Er铝合金的抗拉强度和屈服强度都要高于不含Er铝合金;含Er铝合金相对不含Er铝合金的再结晶温度有明显提高,这主要与合金中Er元素添加后形成了与基体保持共格或者半共格关系的纳米级Al_3Er或者Al_3(Zr,Er)粒子有关。     

喷射电沉积Co-Ni纳米合金沉积层的组织和性能

用高速喷射电沉积法快速制备了块体纳米晶Co-Ni合金,研究了喷镀工艺参数(主盐浓度、电解液喷射速度和电流密度等)对沉积层成分、微观组织结构及性能的影响.结果表明:提高喷射电沉积电解液的搅拌强度能有效减小扩散层的厚度,使电沉积在较高的极限电流密度下进行,提高沉积速度.极限电流密度的增大使阴极过电位增大,从而提高合金的形核速率,使沉积层晶粒的尺寸减小、显微硬度升高.随着电解液中Co2 含量的增加,沉积层中Co含量增加,导致沉积层相结构由单相α-Co(Ni)转变为α-Co(Ni)和ε-Co(Ni)双相组织,并使表面的形貌发生明显的变化.     

An Investigation on Hall-Petch Relationship in Electrodeposited Nanocrystalline Cu-Ni-P Alloys

Nanocrystalline Cu-Ni-P alloys with average grain sizes of 7, 10 and 24 nm were synthesized by means of electrodeposition.The grain size dependences of tensile strength and hardness of the nanocrystalline Cu alloys were investigated.The breakdown of Hall-Perch relation was exhibited in both tensile strength and hardness.     

热处理对AZ31B镁合金轧板组织和性能的影响

研究了AZ31B镁合金轧板经不同温度、时间退火后的组织和性能及其再结晶行为。结果表明,热轧板材在退火过程中主要发生再结晶;退火后,强度略有下降,但伸长率明显提高;在523K下退火,保温60min,可获得平均晶粒直径为10μm的细晶组织,其抗拉强度为258MPa,断裂伸长率为22.3%,综合性能较好。热轧态板材呈脆性准解理断裂,退火后转变为韧性断裂。     

Effect of annealing on tensile properties of electrodeposited nanocrystalline Ni with broad grain size distribution

Abstract

The microstructures and tensile properties of electrodeposited nanocrystalline Ni (nc-Ni) with a broad grain size distribution after annealing at 150, 200 and 300°C for 500 s were investigated. The as deposited broad grain size distribution nc-Ni sample exhibited a moderate strength σ_UTS of ～1107 MPa but a markedly enhanced ductility ?_TEF of ～10%, compared with electrodeposited nc-Ni with a narrow grain size distribution. Annealing below 200°C increased the strength but caused a considerably reduction in tensile elongation. This behaviour is attributed to the grain boundary relaxation and the increased order of grain boundaries after annealing, which can make the grain boundary activities, such as the grain boundary sliding and grain rotations, more difficult. Further annealing at 300°C decreased both the yield strength and tensile elongation significantly due to significant grain growth.     

The effect of annealing on deformation and fracture of a nanocrystalline fcc metal

The tensile deformation and fracture behavior of electrodeposited nanocrystalline Ni–15% Fe alloy samples after annealing for 90 min at 250, 400 and 500 °C temperatures were investigated. The structure of the samples was studied using TEM and XRD techniques and the fracture surfaces were investigated employing SEM. The results of this study indicated that annealing at 250 °C modified grain size distribution slightly but resulted in a significant increase in the initial strain hardening rate. While the average grain size in the 400 °C sample was increased to 59 nm, its yield strength was comparable to the as-deposited alloy with a 9 nm grain size. The plastic tensile elongation of all annealed samples was lowered significantly to less than 1% from approximately 6% in the as-deposited state. These results are discussed in terms of the inhomogeneity of plastic deformation and the evolution of internal stresses in nanocrystalline materials.     

Microstructure and mechanical properties of novel Al-Y-Sc alloys with high thermal stability and electrical conductivity

The microstructure and mechanical properties of novel Al-Y-Sc alloys with high thermal stability and electrical conductivity were investigated.Eutectic Al3 Y-phase particles of size 100-200 nm were detected in the as-cast microstructure of the alloys.Al3 Y-phase particles provided a higher hardness to as cast alloys than homogenized alloys in the temperature range of 370-440℃.L12 precipitates of the Al3(ScxYy) phase were nucleated homogenously within the aluminium matrix and heterogeneously on the dislocations during annealing at 400℃.The average size of the L12 precipitates was 11±2 nm after annealing for 1 h,and 25-30 nm after annealing for 5 h,which led to a decrease in the hardness of the Al-0.2 Y-0.2 Sc alloy to15 HV.The recrystallization temperature exceeded 350℃and 450℃for the Al-0.2 Y-0.05 Sc and Al-0.2 Y-0.2 Sc alloys,respectively.The investigated alloys demonstrated good thermal stability of the hardness and tensile properties after annealing the rolled alloys at 200 and 300℃,due to fixing of the dislocations and grain boundaries by L12 precipitates and eutectic Al3 Y-phase particles.The good combination of strength,plasticity,and electrical conductivity of the investigated Al-0.2 Y-0.2 Sc alloys make it a promising candidate for electrical conductors.The alloys exhibited a yield stress of 177-183 MPa,ultimate tensile stress of 199-202 MPa,elongation of 15.2-15.8%,and electrical conductivity of 60.8%-61.5% IACS.     

Effects of annealing treatment on the ratcheting behavior of extruded AZ31B magnesium alloy under asymmetrical uniaxial cyclic loading

The objective of this investigation is to study the effects of annealing treatment on the ratcheting behavior of extruded AZ31B magnesium alloy. First, the microstructures and monotonic tensile properties of the extruded and annealed alloys were assessed. The results showed that the grain size increased slightly with increasing annealing time until an annealing time of 6 h after which abnormal grain growth happened. Accordingly, the ultimate tensile strength of the Mg alloy decreased with increasing annealing time, while the tensile yield strength and elongation percentage of the Mg alloy increased with annealing time until the annealing time reached 2 h. The cyclic softening/hardening behavior of the annealed AZ31B Mg alloy was similar to that of the extruded alloy: first an apparent cyclic softening was observed, then a cyclic hardening occurred, and finally a stable state was reached. The annealing treatment delayed the occurrence of the cyclic hardening. It was also shown that the effects of the annealing time on the ratcheting strain of the Mg alloy depended of the loading path.     

The formation, structure and properties of nanocrystalline Ni-Mo-B alloys

The structure, structure evolution and microhardness of nanocrystalline Ni-Mo-B alloys were studied by X-ray diffraction, differential scanning calorimetry, transmission and high resolution electron microscopy and microhardness measurements. The nanocrystalline structure was produced by controlled crystallization of amorphous alloys. The annealed samples consist of the FCC nanocrystals with the amorphous regions between them. The grain size of the nanocrystals is about 20 nm and depends on the chemical composition of the alloy. The chemical composition of the amorphous phase between the nanocrystals changes at the annealing. A slight grain growth was observed when the annealing time increases. The diffusion of Mo and B from FCC to the amorphous phase occurs at the annealing. It results in the lattice parameter change. The microhardness of the alloys increases during the annealing. The microhardness values are the same in all alloys before the nanocrystalline structure decomposition. The microhardness is inconsistent with the Petch-Hall equation. The microhardness of the alloys is determined by the microhardness of the amorphous phase bands located between the nanocrystalline grains.     

变形程度对强变形Al-4%Cu合金退火组织性能的影响

为了研究变形程度对强变形Al-4%Cu合金退火行为的影响,通过透射电镜观察和拉伸试验,研究了人工时效Al-4%Cu合金经过不同变形量的多向压缩变形(MAC),退火(120℃/60 min)后的显微组织和力学性能.研究表明:试样中的第二相在MAC过程中破碎溶回基体后,会在后续退火过程中再次析出,且析出相回溶的程度对退火组织性能的影响很大.含θ″相试样和含θ’相试样经MAC变形后,析出相完全回溶于基体,在退火过程中有新的第二相析出,试样强度升高;同时试样的的塑性也得到了提高,这与再析出粒子对超细晶粒长大的阻碍作用有关.析出相未完全回溶的含θ相试样,退火后强度低于退火前,析出相回溶和再析出交替进行.析出相基本回溶态强韧化效果最佳.     

Influence of annealing on the crystallographic structure and some magnetic properties of the Fe73.5Cu1Nb3-xUxSi13.5B9 nanocrystalline alloys

The influence of annealing on the structure and some magnetic properties of Fe73.5Cu1Nb3-xUxSi13.5B9 (x=1, 2, 3) alloys has been studied. The results confirmed the nanocrystalline character of these alloys in the temperature range 550–650 °C. The influence of the uranium content on the structural stability has been observed for annealing treatment at high temperature, i.e. at about 700 °C. The coercive field strongly depended both on the annealing temperature and on the uranium content. A minimum value of Hc was observed after annealing at 550 °C. Core losses of all alloys in the nanocrystalline state decreased with increasing uranium content. © 1998 Kluwer Academic Publishers     

Mechanical behavior of bulk nanocrystalline copper alloys produced by high energy ball milling

Copper alloys with different amounts of zinc were synthesized via high energy ball milling at liquid nitrogen and room temperature. Bulk samples were produced in situ by controlling the milling temperature. It is shown that temperature plays an important role in formation of artifact-free consolidated samples via its effect on defect formation and annihilation during the milling process. The mechanical behavior of Cu–Zn nanocrystalline alloys was examined using Vickers microhardness and tensile tests. The nanostructure of the alloys was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hardness results of processed alloys vary as a function of the alloying elements. Considering typical low ductility of nanocrystalline materials, the improved ductility with the high strength observed in these alloys suggests that they are artifact-free and may have several deformation mechanisms, which may include dislocation activity and nano-twinning.