The influence of quenching and austenitizing temperatures on multiphase evolution, morphology and tensile properties for a low-carbon low-alloy ferritic steel under Q&P&T treatment was investigated in detail in this work. The specimens were characterized using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and tensile tests. The results indicated that the constituent phases in Q&P&T 950 specimens mostly contained numerous refined primary martensite (M-1), lower bainite (LB) and a few blocky retained austenite/secondary martensite (RA/M-2). The content of LB in Q&P&T 950 specimens firstly increased then decreased with increasing quenching temperature from 260 to 300 degrees C, while the content of RA showed a monotonic increasing trend. Length-width ratio of lath-like structure M-1 and plate-like structure LB in Q&P&T1100 specimens firstly increased and reduced as increasing quenching temperature from 260 to 300 degrees C. Length-width ratio of lath-like structure M-1/LB in Q&P&T 1100-280-12 specimen were longer and narrower as compared to Q&P&T1100-260-12 and Q&P&T 1100-300-12 specimens. The UTS and TE increased with the increasing of the length-width ratio of lath-like structure M-1/LB for Q&P&T 1100 specimens with increasing quenching temperature from 260 to 300 degrees C. As compared to Q&P&T 950 specimens, the higher yield strength of Q&P&T 1100 specimens may be related to the microstructure refinement strengthening, dislocation strengthening, precipitation strengthening due to the precipitation of fresh carbides and solution strengthening due to the dissolution of carbides.

The effect of austenitization temperature and partitioning/tempering time on microstructural evolution during quenching-Partitioning-Tempering (Q&P&T) treatment was investigated. The results showed that multiphase microstructure consisting of primary martensite, lower bainite, filmy/blocky retained austenite, and carbide precipitation were produced in low-alloy ferritic steel. A total of 36 regimes with the austenitization temperature 950 degrees C and 1100 degrees C, the quenching temperature of 260 degrees C, 280 degrees C and 300 degrees C, the partitioning temperatures of 400 degrees C, and partitioning time of 2-62 minutes were applied. In this study, Vickers hardness measurements were utilized to assess the mechanical properties of metallic materials. Through TEM characterization and selected area electron diffraction, key findings include: Filmy retained austenite exhibited high stability due to carbon enrichment, whereas blocky retained austenite partially transformed into twinned martensite containing omega-phase, revealing a trade-off between strengthening effects and ductility loss; Phase transformation strain during quenching/partitioning triggered {112}< 111 > twinning, with omega-phase reverse transformation (HCP -> BCC) driving the twinning mechanism via elastic bending and short-range diffusion. This work provides a process design framework for developing low-alloy steels with combined high strength and toughness.

Particle-reinforced Ni-P composite coatings exhibit promising mechanical properties, yet further enhancement remains key for broader applications. In this study, Ni-P-Al2O3-PTFE nanocomposite coatings prepared via jet electrodeposition under varying current densities and plating temperatures were systematically investigated. Xray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy reveal optimal nanoparticle incorporation and smooth surface morphology at a current density of 20 A center dot dm- 2 and a plating solution temperature of 50 degrees C. Under the optimal conditions, the coating exhibits a deposition rate of 59.51 mu m center dot h- 1, a microhardness of 695 HV, an average friction coefficient of 0.16, and a minimum surface roughness of 77 nm, respectively-primarily due to refined grains and enhanced dispersion strengthening from increased nanoparticle content. Tribological analysis indicates superior wear resistance and toughness, evidenced by a lower friction coefficient and higher elastic recovery. These findings clarify the interplay between deposition parameters and coating performance, providing technical guidance for the fabrication of wear-resistant and toughened Ni-P-Al2O3-PTFE coatings via jet electrodeposition. This study underscores the potential of optimizing current density and temperature to achieve advanced nanocomposite coatings for industrial applications.

In this paper, effect of various contents of chitosan (1.0, 1.5 and 2.0 wt%) on corrosion/degradation behavior of ternary HA-NrGO-CS prepared on ZK60 alloy substrates were investigated. The samples were prepared by combining cathodic electrophoretic deposition and thermal argon atmosphere annealing for 120 min at 200 degrees C to regulate corrosion and quick degradation of ZK60 Mg alloy surface. After immersion for 30 min, HA-NrGO-1.5CS coated sample exhibited highest |Z| 0.1Hz value, trailed by the HA-NrGO-2.0CS, HA-NrGO-1.0CS and ZK60 alloy samples. After immersion for 2 days, |Z| 0.1Hz values moved to higher Bode modulus for HA-NrGO-CS coated samples, indicating poles and defects were filled due to the formation of apatite layer on the HA-NrGO-CS surface. FT-IR and Raman spectra proved the successful doping of N atoms into the rGO nanosheet skeleton to form NrGO. The SEM images and EDS plane-scan results for the samples after immersion for 2 days verified the existence of an apatite layer. The experimental results indicated that the existence of CS, HA and NrGO in the composite coatings can regulate the pH values and supply a sustained release of Mg2+ 2+ ions and O2 2 due to the synergistic effect of the protonation/deprotonation of-NH2 2 groups in CS and the dissolution/recrystallization of HA. Furthermore, the production of MgO2 2 film can convert corrosion behavior of ZK60 alloy from pitting corrosion to uniform corrosion, which provided a potential strategy for bone biomedical applications.

氧化石墨烯(graphene oxide,GO)是一种理想的二维纳米材料,具有独特的片层结构和阻隔性能,被广泛应用于高阻隔材料、化工和医学等领域.但GO加入聚合物中时会发生聚集和团聚,因此要在GO中加入不同的分散剂,以提高含GO的涂层的密度和改善其缓蚀效果.目前常用的分散剂有纯溶剂、壳聚糖、硅烷偶联剂和聚合物等.

HA-GO/MgF2 composite coating was prepared via a pretreatment of acid solution followed by electrophoretic deposition on AZ91D Mg alloy substrate, subsequently thermally reduced to obtain HA-RGO/MgF2 double layered composite coating. The effect of the content of RGO on the surface morphology, crystalline structures and corrosion resistance of the composite coating were evaluated. The results showed that RGO contents in the suspensions was 0.33 mg/mL, the resulting HA-RGO-0.33/MgF2 composite coating exhibited uniform and dense surface morphology, with excellent bonding to the AZ91D Mg alloy substrate. Electrochemical tests revealed that HA-RGO/MgF2 composite coating improved the corrosion resistance of AZ91D Mg alloy substrate, which mainly due to RGO can act as a fence for the corrosive ions in the SBF solution to penetrate into the composite coating through filling up pores and micro-cracks present in the composite coating. Immersion tests of the coated samples in SBF also showed that HA-RGO-0.33/MgF2 composite coating can improve the corrosion resistance of AZ91D Mg alloy substrate during the immersion of 5 days. The obtained results suggested that the HA-RGO/MgF2 double layered composite coatings possess good formation ability of apatite in the SBF solution, which were related to RGO provides favorable sites for apatite nucleation. Based on the experimental results, the corrosion mechanism of HA-RGO/MgF2 composite coating and AZ91D Mg alloy substrate was proposed.

镁合金存在腐蚀速度过快以及打磨后表面因其光滑平整而无法直接沉积涂层的问题.使用HF处理后,表面具有一定的粗糙度,有利于沉积层的附着.同时,HF处理后的镁合金表面会生成一层致密的氟化镁(MgF2)化学层,更加提高了对于腐蚀介质的抵抗作用.本研究采用电泳沉积的方法在镁合金表面制备羟基磷灰石(HA)-氧化石墨烯(GO)复合涂层.随后热处理,使GO转变为还原氧化石墨烯(RGO).通过设置悬浮液中GO的不同含量,以探究RGO含量对HA-RGO/MgF2复合涂层形貌和耐腐蚀性的影响.结果表明,当GO含量为0.33 mg/mL时,HA-RGO/MgF2复合涂层具有最佳耐腐蚀性.

HA-rGO-ZnO ternary composite coatings were successfully prepared on ZK60 magnesium alloy using cathodic electrophoretic deposition method. XRD analysis proved the addition of ZnO nanoparticles induced a signifi-cantly reduced crystallinity in hydroxyapatite and the tensile strain values of HA-rGO-ZnO composite coatings gradually decreased as the content of ZnO increased. SEM analyses revealed that the HA and ZnO nanoparticles were anchored on rGO nanosheets and a closely-packed network of recrystallization needle-like ZnO and mineralization HA crystals was formed on the surface of HA-rGO-ZnO coated sample. The resulting composite coating exhibited a uniform and compact HA-rGO-16ZnO composite coating, with well adhered to the ZK60 magnesium alloy substrate. The HA-rGO-16ZnO coated sample exhibited the highest corrosion resistance with lowest icorr (1.12 x 10-6 A/cm2) and the highest Ecorr (-1.43 V/SCE) value when compared to HA-rGO-14ZnO and HA-rGO-18ZnO samples after immersion in a SBF for 10 min. Compared to HA-rGO-ZnO coated samples after 10 min of immersion in SBF, HA-rGO-ZnO coated samples after 3 days of immersion in SBF exhibited a remarkably improved corrosion resistance and rapid inducing of the apatite layer precipitated on the surface of the composite coatings. The microstructure and composition for the coated samples after 3 days of immersion in SBF also confirm that the presence of a apatite layer on the composite coatings. HA-rGO-18ZnO coated samples after 3 days of immersion in SBF showed the lowest icorr value, which indicating HA-rGO-18ZnO ternary com-posite coatings dramatically improved the formation ability of the apatite layer and led to an enhancement in the bioactivity. Accordingly, it is believed that the HA-rGO composite coating incorporated with ZnO will be a potential candidate for bone biomedical applications.

The concurrent (Fe,Mo)(2)C carbides and Cu-rich clusters precipitation in the ferritic steel containing copper after aging at 400 degrees C for 4000 h have been investigated using transmission electron microscopy (TEM) and atom probe tomography (APT). The results show that spinodal decomposition and an atomic ordering reaction occur in the ferritic steel containing copper. After aging, the retained austenite decomposed by the spinodal mechanism into C-rich and C-lean regions. The C-rich phase transforms into the (Fe,Mo)(2)C carbides via the ordering reaction, while Cu-rich clusters formed in the C-lean regions. The experimental results can be interpreted on the basis of phase separation via spinodal decomposition followed by chemical ordering. The small size of Cu-rich clusters can be attributed to the lower diffusion coefficient of Cu in the retained austenite.

Electrochemical additive manufacturing (ECAM) based on electrochemical deposition (ECD) has been increasingly used, owing to its inspiring capacities of fabricating void-free and crack-free three-dimensional (3D) complex dense nano-and micro-sized metal geometries. In this study, a unique electrolyte-column localized electrochemical deposition (ECL-ECD) was initially proposed to manufacture 3D intricate precision micro-and mesoscale solid objects. In ECL-ECD, a dynamically stable electrolyte column is maintained between the electrolyte nozzle (anode) and cathodic surface, and metal electrodeposition is localized and guided by the electrolyte column, which is moved controllably. Its working mechanisms were determined from simulations and experimental findings, and some intricate structures such as curved columnar structures, U-shaped, Z-shaped, and spiral structures were successfully manufactured via the proposed technique using different path planning and control strategies. It was indicated that ECL-ECD has an excellent capacity in additively manufacturing micrometer-to-millimeter-scale freestanding metal geometries simultaneously with relatively high geometrical accuracy, good surface finish, and material compactness. ECL-ECD, as a novel metal additive manufacturing (AM), is significantly competitive in micro and mesoscale metal manufacturing, filling the gap in mesoscale ECAM technology.

Additive electrochemical micro-manufacturing (micro-AECM) is a nontraditional fabrication method which fundamentally employs electrochemical deposition (ECD) mechanism in different forms to manufacture metal based microstructures layer-upon-layer. Micro-AECM based on traditional mask-based ECD has long been widely adopted to manufacture large scale precision two-dimensional (2D) and quasi-three-dimensional (quasi 3D or 2.5D) metallic micro-sized geometries by inversely duplicating the photoresist though-masks patterned lithographically. Recently, micro-AECM has attracted increasing attention owing to its significant potential advantages in producing 3D complex void-free and crack-free microstructures with a favorable surface finish and now has emerged as a true additive micro-manufacturing (electrochemical additive manufacturing) technology based on ultrafine anode/electrolyte-jet-induced ECD (maskless micro-AECM). To date, several micro-AECM techniques have been developed to meet versatile applications, and some of them have already been used commercially. In this paper, the fundamental schematic of ECD closely related to micro-AECM is introduced, and several typical micro-AECM techniques are reviewed, including through-mask electroplating, instant masking (IM) plating, electrochemical fabrication (EFAB), localized electrodeposition (LECD), jet electrochemical deposition (Jet ECD), meniscus-confined electroplating (MCED), electrohydrodynamic redox printing (EHD-RP), tip based nanofabrication (TBN), and fluidic force microscope electrodeposition (FluidFM electrodeposition). Furthermore, the challenges, development trends and perspectives of micro-AECM are discussed.

为了解预防老年人跌倒及跌伤服装的发展,分析老年人对跌伤防护服装的需求,列举了视频图像分析法、音频信号分析法和可穿戴传感技术分析法及其应用原理和优缺点,重点分析弹性缓冲材料、压缩气室空气变形材料及新型冲击硬化高分子材料在跌伤防护服装领域的应用形式,总结国内外防护产品的代表性研究成果及其与服装的结合方向,指出开发老年人跌伤防护服装的注意事项,得出应从服装款式与结构,服装舒适性、美观性及安全性,服装智能化3个方面综合考虑老年人防跌伤服装的发展趋势.

Kerosene-submerged jet electrochemical machining (Jet-ECM) has been proven to be an effective process to enhance the machining localization of Jet-ECM. However, this process can only show its best capabilities and advantages under appropriate electrochemical machining parameters. Its machining effects will be weakened when the workpiece surface is relatively large or electrolytic products generated during machining are quite more, which may cause the electrolyte and electrolytic products to accumulate on the workpiece surface, thereby affecting its mass transfer environment. Therefore, for further improving its process capabilities, it is necessary to eliminate the accumulation of electrolyte and electrolytic products on the workpiece surface. And thus, this paper focuses on optimizing its electrochemical machining parameters and investigating the surface effect and shape effect of the workpiece on its machining localization and machining accuracy experimentally and theoretically. It was found that the surface effect and shape effect of the workpiece has a significant influence on its machining localization and machining accuracy. And kerosene medium instead of air medium surrounding the electrolyte-jet can improve the machining localization of Jet-ECM. Besides, compared with traditional Jet-ECM, kerosene-submerged Jet-ECM can produce high accuracy microstructure with a smooth surface. Additionally, micro-sized features fabricated by Jet-ECM on the small surface flat workpiece and curved surface workpiece feature higher machining accuracy and better surface quality than the large surface flat workpiece.

Hydroxyapatite (HA)-graphene oxide (GO) composite coatings reinforced with various rare earth (RE) metal oxide (La2O3 and Y2O3) of composite coatings are electrophoretic deposited on AZ91 magnesium alloy substrate. The effects of RE metal oxide on the composition, surface morphology and corrosion behavior of HA-GO composite coatings in the solution of 0.9 wt. % have been systemically investigated. According to the experimental results, HA-GO-Y2O3 composite coating had displayed superior performance of corrosion prevention in 0.9 wt. % NaCl solution. Considering the results of EIS, microstructures, the surface porosity and the RE metal oxide in the HA-GO composite coatings. Taking the roles of the formation of HA-GO-RE complexes in pores/cracks of HA-GO composite coatings at the composite coatings/ the Mg (OH)(2) film interface in the corrosion mediums into account, the precipitation of precipitated HA-GO-RE protective film is a reasonable explanation for the corrosion resistance of AZ91 Mg alloy. The experimental results manifested that the effects of the microstructures and porosity, the formation of HA-GO-RE complexes in pores/cracks and Cl- concentration in NaCl solutions on improving corrosion resistance of AZ91 Mg alloy exhibited obviously synergistic effects.

Carbonated hydroxyapatite-graphene oxide (GO) composite coatings were obtained on AZ91 magnesium alloy using electrophoretic deposition from isopropanol suspensions. The results showed that ultrasonic treatment exfoliated GO sheets and promoted CO2 adsorption on the surface of GO sheets. Subsequently, B-type carbonated HA was generated during ultrasonication-assisted EPD. The experimental results manifested that microstructures and porosity, carbonated HA content and the formation of GO-Mg complexes in pores/cracks had a significant synergistic effect on improving corrosion resistance of AZ91 magnesium alloy. HA-GO-0.33 composite coating had shown superior performance of corrosion prevention in the 0.9 wt. % NaCl solution which provided some corrosion theoretical basis for the application of Mg alloy in the direction of human implantation.

为探究充气面料对老年人跌倒能否起到缓冲作用,以及影响其抗冲击性能的因素.采用一款热压充气面料,利用医用假人对有无充气面料、不同面料花型及同一花型不同充气厚度的面料样品进行抗冲击测试.结果 表明:充气面料能起到一定缓冲作用;不同的热压花型对充气面料的缓冲作用有较大影响;同一花型,受其形状大小和气室容纳的空气量影响,充气面料的抗冲击效果会呈现不同变化.根据实验结果选取最优充气面料,为老年人跌倒防护服装的开发提供一种新的思路.

To improve the deposition accuracy and surface quality of the deposited micro-features, a novel compressed air-film encircling Jet ECD was proposed. In the proposed Jet ECD, a high-speed compressed air-film is coaxially encircling the impinging electrolytic jet. Numerical model describing the coupled field of electric field and flow field was established, and some auxiliary observations and measurement experiments were conducted to investigate the distribution characteristics of electric field and hydrodynamics characteristics in the concerned regions as well as the change of the electrolyte jet diameter. And the effect of air-film formation parameters and hydrodynamic parameters of the electrolyte jet on the electrodeposition behaviors during forming patterns and high aspect ratio micro-features were studied. Deposition accuracy and surface quality of the microstructures fabricated by the compressed air-film encircling Jet ECD were evaluated. It was demonstrated that, compared with the traditional Jet ECD, the proposed Jet ECD has a higher deposition accuracy and faster deposition rate (up to 1 mu m s(-1)) as well as better surface quality. In addition, the newly developed Jet ECD has an admirable additive manufacturing ability and a 370 +/- 3 mu m-diameter smooth column with the aspect ratio of about 20 was successfully manufactured. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

The tensile fracture behavior of 55CrSi spring steels were investigated. The results demonstrate that interior inclusion and hydrogen level has a significant effect on ductility and a minimal effect on tensile strength of the spring steel. It was due to the effect of cracking from MgO-Al2O3 spinel inclusion or the inclusions with a mixture of CaO, SiO2 and part of Al2O3 due to hydrogen. The results of SEM showed that the ductility reduction is connected with the formation of ‘fisheye’ which formed under the influence of mobile hydrogen. For the specimen containing MgO-Al2O3 spinel inclusion, the fracture surface in the ‘fisheye’ area is mainly composed of three regions including typical quasi-cleavage mixed intergranular fracture, dimple mixed transgranular fractures and ductile fracture from the interior to the edge, whereas there is no obvious transition zone from brittle fracture to dimple fracture in the ‘fisheye’ area of the specimen containing inclusions with a mixture of CaO, SiO2 and part of Al2O3.

在甲烷气氛中,采用电泳沉积技术在尺寸为20 mm×20 mm×3 mm的Inconel600高温合金试样上制备了含镍和铝的氧化钇稳定氧化锆复合涂层,一种热障涂层.通过XRD、SEM和1100℃氧化试验研究了甲烷气氛和镍与铝的摩尔比对复合涂层(YSZ/(Ni,Al))的微观组织和抗高温氧化性能的影响.结果 表明:在甲烷气氛中1100℃烧结2 h后,YSZ/(Ni,Al)复合涂层中形成了ZrC,能提高涂层的致密度和抗高温氧化性能;YSZ/(Ni,Al)涂层中AlNi3相在1100℃氧化生成Al2O3相,将填充涂层中的孔洞和裂纹,并促进其自愈合,从而进一步提高了涂层的抗高温氧化性能.镍与铝的摩尔比为1:3和1:2的YSZ/(Ni,Al)复合涂层具有良好的抗高温氧化性能.

提出一种近阴极周向平动搅拌式电铸技术,通过数值仿真分析了搅拌板的周向平动半径(R)及其与阴极面的距离(h)对近阴极面液流层分布特性的影响,并开展了工艺验证试验.结果表明:搅拌板的周向平动运动参数对电铸层厚度均匀性有显著影响.在优化的条件(h=1.5 mm,R=10 mm,平动周期T=4 s)下所得电铸层(面积为150 mm×150 mm)的厚度约为75μm,均匀性达91.5％,不过边缘区的电铸层偏厚.数值仿真所得的电铸层厚度分布影响规律与316不锈钢表面电铸镍的实验结果基本一致.