Influence of Ag content on the microstructure,mechanical, and tribological properties of TaVN–Ag films

A series of TaVN–Ag nanocomposite films were deposited using a radio-frequency magnetron sputtering system. The microstructure, mechanical properties, and tribological performance of the films were investigated. The results showed that TaVN–Ag films were composed of face-centered cubic(fcc) TaVN and fcc-Ag. With increasing Ag content, the hardness of TaVN–Ag composite films first increased and then decreased rapidly. The maximum hardness value was 31.4 GPa. At room temperature, the coefficient of friction(COF) of TaVN–Ag films decreased from 0.76 to 0.60 with increasing Ag content from 0 to 7.93 at%. For the TaVN–Ag films with 7.93 at% Ag, COF first increased and then decreased rapidly from 0.60 at 25℃ to 0.35 at 600℃, whereas the wear rate of the film increased continuously from 3.91 × 10-7 to 19.1 × 10-7 mm~3/(N·mm). The COF of the TaVN–Ag film with 7.93 at% Ag was lower than that of the TaVN film, and their wear rates showed opposite trends with increasing temperature.     

Characterization of Cu-Ti powder metallurgical materials

Powder metallurgical Cu-Ti alloys with different titanium additions produced by hot pressing were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and hardness, wear and bending tests. The addition of titanium to copper caused the formation of different intermetallic layers around titanium particles. The titanium content of the intermetallics decreased from the center of the particle to the copper matrix. The hardness, wear resistance, and bending strength of the materials increased with increasing Ti content, whereas strain in the bending test decreased. Worn surface analyses showed that different wear mechanisms were active during the wear test of specimens with different chemical compositions. Changes in the properties of the materials with titanium addition were explained by the high hardness of different Cu-Ti intermetallic phases.     

Wear Resistance and Structure of Electrodeposited RE-Ni-W-P-SiC-PTFE Composite Materials

Effects of heat treatment temperature and time on hardness and wear resistance of RE-Ni-W-P-SiC-PTFE and RE-Ni-W-P-SiC composite coatings were studied. The results indicated that the hardness of the composite coatings as-deposited was lower and the mass loss (i.e. rate of abrasion) was higher, while the hardness increased and the rate of abrasion decreased with the increase of heat treatment temperature. The rate of abrasion was the lowest and hardness was the highest at 400℃ . The hardness decreased and the rate of abrasion increased with the temperature increasing continuously. Both the hardness and wear resistance also increased with the prolongation of heat treatment time, reaching their peak values when the heat treatment time was 2 h. The experimental results also showed that the hardness of the coatings decreased with PTFE quantity enhancing, but the wear rate diminished correspondingly. X-ray diffraction analysis indicated that the structure of RE-Ni-W-P-SiC-PTFE composite coating as-deposited is amorphous, and it partly became crystal when heat treatment temperature was over 3000℃.     

Martensitic transformation and magnetic properties of aged Ni-Fe-Ga-Ti shape memory alloy

This article reports the effect of ageing on the microstructure, martensitic transformation, magnetic properties, and mechanical properties of Ni₅₁Fe₁₈Ga₂₇Ti₄ shape memory alloy. There are five specimens of this alloy aged at 573 up to 973 K for 3 h per each. This range of ageing temperature greatly affects the microstructure of the alloy. As the ageing temperature increased from 573 up to 973 K, the microstructure of Ni₅₁Fe₁₈Ga₂₇Ti₄ alloy gradually changed from the entirely martensitic matrix at 573 K to the fully austenitic microstructure at 973 K. The volume fraction of precipitated Ni₃Ti particles increased with the ageing temperature increasing from 573 to 773 K. Further increasing the ageing temperature to 973 K decreased the content of Ni₃Ti in the microstructure. The martensitic transformation temperature was decreased steadily by increasing the ageing temperature. The magnetization saturation, remnant magnetization, and coercivity increased with the ageing temperature increasing up to 773 K. A further increase in ageing temperature decreased these magnetic properties. Moreover, the hardness values were gradually increased at first by increasing the ageing temperature to 773 K, and then dramatically decreased to the lowest value at 973 K.     

Tailoring of microstructure and martensitic transformation of nanocrystalline Ti–Ni-Hf shape memory thin film

The amorphous Ti-Ni-Hf thin films with the specific compositions were prepared from single Ti-Ni-Hf alloy target by adjusting processing parameters of direct current magnetron sputtering deposition. Prior to the crystallization,a glass transition occurred in the present Ti-Ni-Hf thin films. The annealed Ti-Ni-Hf thin films were characterized by the nano-crystalline. With the annealing temperature increasing, the grain size firstly increased and then decreased owing to the presence of(Ti,Hf)_2Ni precipitate. Two endothermic and exothermic peaks corresponding to B19'■B2 martensitic transformation in heating and cooling curves were observed for the Ti-Ni-Hf thin films with the lower annealing temperature and shorter annealing time, which was closely related to the inhomogeneous composition. However, the Ti-Ni-Hf thin films annealed at higher annealing temperature and longer annealing time showed the single stage B19'■B2 martensitic transformation. In addition, the martensitic transformation temperatures firstly increased and then decreased with the annealing temperatures rising.     

Effects of Gd solutes on hardness and yield strength of Mg alloys

Relative contribution of individual strengthening mechanisms to the yield strength of Mg–0–15 wt%Gd alloys were investigated.Alloys with different grain size were prepared by adding Zr and hot extrusion.Hardness and tensile/compression yield strength were tested on the alloys after solid solution treatment and extrusion.HallPetch constants were calculated with hardness and tensile/compressive data.The results showed that the hardness of Mg–Gd alloys with similar Gd content and different grain size were almost the same,which indicates that grain size had little effect on hardness.The hardness linearly increased with rising Gd content(d H_v/dc≈25 kg mm~(-2)/at%Gd).The tensile and compressive yield strengths enhanced with the increase of Gd content for all alloys in different conditions.In addition,the tensile/compressive(t/c)yield asymmetry of extruded alloys decreased with increasing Gd content.Large t/c yield asymmetry ratio(1.77)was observed for pure Mg,and with increasing Gd content this value decreased to 1.With the increasing of tensile strength,the stress intensity factor,k_y,decreased from 0.27 MPa m~(1/2)for Mg–2 wt%Gd alloy to 0.19 MPa m~(1/2) for Mg–5 wt%Gd alloy,then increased to 0.29 MPa m~(1/2) for Mg–15 wt%Gd alloy.However,k_yincreased linearly form 0.16–0.31 MPa for compression test.The influence of grain size strengthening was eliminated,and the yield strength of tension and compression both linearly increased with c~n,where c is the atom concentration of Gd,and n=1/2 or 2/3.     

Microstructure and mechanical properties of SiC-particle-strengthening tri-metal Al/Cu/Ni composite produced by accumulative roll bonding process

In this study, a multilayer Al/Ni/Cu composite reinforced with SiC particles was produced using an accumulative roll bonding (ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements (Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.     

Microstructure and mechanical properties of Cr doped WCoB based cermets by spark plasma sintering and first principle calculation

WCoB based cermet is a potential hard alloy to replace WC-Co cermets with high hardness and corrosion resistance. WCoB based cermets with different Cr doping contents were fabricated by spark plasma sintering in liquid phase sintering stage. The densification behavior, phase composition, microstructure and mechanical properties of Cr doped WCoB cermets were investigated by XRD, EDS and SEM. Due to the lower density of Cr,the density of WCoB cermets decreased with the increasing of Cr doping content. The phase composition consisted of Cr doped WCoB, unreacted W, Co–Cr binary binder phase. When the doping content exceeded11.736 wt%, the Cr enrichment zones appeared, which was harmful to the TRS. The increasing of Cr doping content contributed to the increase of unreacted W phases content and the formation of pores. The maximum value of Vickers hardness was 1751 Hv0.5 at 9.356 wt% Cr doping content. The variation trend was explained by first principle calculation, which is consistent with Hv-Zhou hardness model.     

Relationship between the specific surface area of rust and the electrochemical behavior of rusted steel in a wet-dry acid corrosion environment

The relationship between the specific surface area (SSA) of rust and the electrochemical behavior of rusted steel under wet-dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O₂ into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O₂ and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3sf</Subscript> addition on the friction and wear properties of (SiC<Subscript>p</Subscript>+Al<Subscript>2</Subscript>O<Subscript>3sf</Subscript>)/Al2024 composites fabricated by pressure infiltration

Aluminum (Al) 2024 matrix composites reinforced with alumina short fibers (Al₂O_3sf) and silicon carbide particles (SiC_p) as wear-resistant materials were prepared by pressure infiltration in this study. Further, the effect of Al₂O_3sf on the friction and wear properties of the as-synthesized composites was systematically investigated, and the relationship between volume fraction and wear mechanism was discussed. The results showed that the addition of Al₂O_3sf, characterized by the ratio of Al₂O_3sf to SiC_p, significantly affected the properties of the composites and resulted in changes in wear mechanisms. When the volume ratio of Al₂O_3sf to SiC_p was increased from 0 to 1, the rate of wear mass loss (K_m) and coefficients of friction (COFs) of the composites decreased, and the wear mechanisms were abrasive wear and furrow wear. When the volume ratio was increased from 1 to 3, the COF decreased continuously; however, the K_m increased rapidly and the wear mechanism became adhesive wear.     

[Ag／CoPt]n／Ag薄膜的结构和磁性

采用磁控溅射方法在玻璃基片上制备了[Ag／CoPt]n／Ag薄膜,并在600℃退火30min．结果表明,Ag掺杂厚度（x）对CoPt薄膜的结构和磁性影响很大．当Ag层厚度为0．5nm时,薄膜的垂直取向程度最高,其垂直矫顽力高达8．68×10^5A·m^-1而平行矫顽力仅为0．54×10^5A·m^-1．适当厚度的Ag不仅有利于薄膜的垂直取向,而且能降低晶粒间的交换耦合作用．     

磁控溅射制备Ag/TiO2复合薄膜的光催化降解性能

为了提高TiO2薄膜的光催化效率,利用中频交流磁控溅射技术,采用Ti和Ag金属靶制备了Ag/TiO2复合薄膜.利用X射线光电子能谱、 X射线衍射和扫描电子显微镜分析了复合薄膜的成分、结构和表面形貌,并研究了其光催化降解性能.结果发现: Ag在厚度较薄时以聚集颗粒形式存在; 在Ag膜厚度为15 nm时, Ag/TiO2复合薄膜与TiO2薄膜相比其光催化效率可提高2倍; Ag/TiO2复合薄膜对亚甲基蓝的光催化降解效率与复合薄膜的透射率均随Ag膜厚度增加逐渐下降,其原因是Ag膜厚度不断增加,最终完全覆盖TiO2薄膜表面,阻挡了TiO2薄膜与污染物的有效接触, Ag作为光生电子捕获剂的有利影响消失.     

TaAgN复合膜显微结构、力学性能和摩擦性能的研究

采用非平衡反应磁控溅射法制备了TaAgN复合膜。利用X射线衍射仪、CSM纳米压痕测试仪和摩擦磨损测试了复合膜的显微结构、力学性能和摩擦性能。结果显示,TaAgN复合膜由面心立方结构的TaN相和底心斜方结构的Ta₄N相组成。随着Ag靶功率的增加,硬度H、弹性模量E、弹性恢复W_e和H³/E²值均呈先升高后降低的趋势,最大值分别为34 GPa,394 GPa,57%和250 MPa。随着Ag靶功率的增加,TaAgN复合膜室温下的平均摩擦因数呈降低趋势。当Ag靶功率为25 W时,随着温度的升高,TaAgN复合膜的平均摩擦因数逐渐减小。     

纳米SiC增强铝合金表面阳极氧化膜的组织与性能

以硫酸、草酸、氨基磺酸为基础电解液,分别添加3,8,12,15 g/L的纳米SiC颗粒,利用直流氧化电源在优化的复合共沉积工艺参数下,在2024铝合金表面制备纳米SiC增强的硬质阳极氧化膜.结果表明:纳米SiC颗粒弥散分布在阳极氧化膜中,形成了纳米颗粒增强的硬质Al2O3氧化膜组织结构;随着纳米SiC添加量的增加,膜的厚度由没有添加纳米SiC颗粒的42μm增加到了48μm;当SiC的添加量为12 g/L时,氧化膜的硬度最高而磨耗最低,硬度由没有添加纳米颗粒样品的400 HV左右提高到了440 HV,磨损量由25 mg降到8 mg;纳米SiC在阳极氧化过程中,通过机械夹杂、吸附作用等形式进入膜层...     

不同环境温度下典型身管用钢磨损性能研究

通过摩擦磨损、高温硬度及相应的分析试验研究了典型身管用钢32Cr2MoVA、30SiMn2MoVA在室温、200、400以及600℃下的摩擦磨损行为与规律.结果表明:两种材料的摩擦系数在各个温度区间内的区别不大,主要受摩擦氧化物产生与否影响.32Cr2MoVA的磨损率随着温度的提高先降低再提高之后又下降,30SiMn2MoVA的磨损率随着温度的上升而先降低,然后逐渐升高,600℃达到最高.温度、身管钢在高温下的硬度和磨盘材料与滑动销的高温硬度差(Hd--Hp)共同影响磨损表面氧化物层的最终形态.室温至200℃时,身管钢磨损行为主要受表面氧化物层的影响.室温下两种身管钢磨损机理均为黏着磨损及磨粒磨损,200℃时均为氧化轻微磨损.环境温度达到400℃以上时,身管钢以及磨盘材料的基体硬度开始影响磨损行为.400℃时两种身管钢磨损机理均为氧化严重磨损.600℃时,32Cr2MoVA的Hd--Hp减小,磨损表面出现了厚度很大、致密的氧化物层,磨损机理为氧化轻微磨损;而30SiMn2MoVA的Hd--Hp显著增大,试样发生了明显的塑性挤出,为塑性挤出磨损.     

纳米银溶胶中超痕量分子的Raman光谱

根据柠檬酸钠还原硝酸盐的原理制备直径为80~90 nm的银纳米颗粒溶胶, 采用1 mW激光功率和5 s积分时间, 通过表面增强Raman散射技术检测到浓
度为10^-13 mol/L水中的超痕量若丹明6G分子, 通过制备银纳米膜的方法检测到浓度为10^-11 mol/L的超痕量R6G分子. 实验结果表明, 若银纳米颗粒的密度降低, 则其增强Raman散射的能力减弱.     

WC的质量分数对喷熔层耐磨性能的影响

在自熔性合金粉末Ni60中机械混合不同质量分数的WC进行火焰喷熔,通过喷熔工艺性能试验、喷熔层宏观硬度测试、喷熔层低应力磨粒磨损试验、喷熔层冲击磨粒磨损试验和显微组织分析,研究了w(WC)对喷焊层耐磨性能的影响。试验证明:随着合金粉中w(WC)的增大,喷焊工艺性能变差,但当w(WC)低于50%时,WC的加入对喷焊工艺性能影响不很明显,喷熔层硬度变化不大,喷熔层低应力磨粒磨损性能随w(WC)的增大而提高;当w(WC)大于50%时,WC的加入使喷熔工艺性能变得极差,喷熔层的硬度和耐低应力磨粒磨损性能降低。由于WC硬而脆的性能和在喷熔层显微组织中起分割基体的作用,喷熔层耐冲击磨粒磨损性能随w(WC)的增大而降低。     

石墨烯/水性聚氨酯复合涂层的制备与性能改善

采用二苯胺磺酸钠(DPS)制备石墨烯水分散液,然后与水性聚氨酯乳液物理共混,干燥后制备出石墨烯/水性聚氨酯复合涂层.结果表明:DPS能够对石墨烯起到良好的分散作用;并且随着石墨烯用量的增加,复合涂层的抗静电性、力学性能、耐高温性、耐水性和耐酸碱性得到有效提高.复合胶膜与纯水性聚氨酯胶膜相比,其表面电阻率从8.64×1012Ω降低至5.54×108Ω,拉伸强度从13.71 MPa增加至17.32 MPa,吸水率由10.33%降低至3.87%,吸酸碱溶液率分别由8.68%和9.36%降低至2.93%和3.84%,硬度提高6.29%,碳化温度提高65℃.     

淬火分配处理对高碳钢组织、力学性能和磨损性能的影响

The present work employed the X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, and electron probe microanalysis techniques to identify the microstructural evolution and mechanical and abrasive behavior of high carbon steel during quenching-partitioning treatment with an aim to enhance the toughness and wear resistance of high carbon steel. Results showed that, with the increase in partitioning temperature from 250 to 400°C, the amount of retained austenite (RA) decreased resulting from the carbide precipitation effect after longer partitioning times. Moreover, the stability of RA generally increased because of the enhanced degree of carbon enrichment in RA. Given the factors affecting the toughness of high carbon steel, the stability of RA associated with size, carbon content, and morphology plays a significant role in determining the toughness of high carbon steel. The analysis of the wear resistance of samples with different mechanical properties shows that hardness is the primary factor affecting the wear resistance of high carbon steel, and the toughness is the secondary one.     

The influence of the nonmagnetic metal spacer Bi, Ag and Cu on the properties of the multilayer films

When a ferromagnetic (FM)/antiferromagnetic (AFM) bilayer is field-cooled below the Neel temperature (TN) of the AF layer, a unidirectional anisotropy is induced in the FM. Exchange bias is one of the phenomena as- sociated with the exchange anisotorpy cr…