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The accumulation of debris between the inter-electrode gap caused by inefficient flushing during the micro-electrical discharge machining (micro-EDM) process leads to severe tool electrode wear and decreases the machining accuracy of micro-holes. In this study, a novel method using tool electrode spiral motion feed mode combined with fixed reference axial compensation (FRAC) is proposed to promote the debris evacuation and improve the machining accuracy of micro-holes. Different depths of micro-holes in titanium alloy were drilled using the tool electrode linear motion feed mode and spiral motion feed mode combined with FRAC and without compensation. The process parameters were optimized and determined by means of response-surface experiments to improve machining accuracy and machining efficiency. The results showed that the tool electrode spiral motion feed mode can improve the debris evacuation more effectively than the tool electrode linear motion feed mode. The micro-holes without cone at the bottom could be fabricated using the tool electrode spiral motion feed mode. The introduction of FRAC could improve the depth error of micro-holes furtherly. A high accuracy micro-hole with a depth error of only 0.21% could be fabricated efficiently under the condition of the optimal process parameters. The tool electrode spiral motion feed mode combined with FRAC has an obvious advantage in the fabrication of high accuracy micro-holes during the micro-EDM process. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured Al2O3-40%YSZ (AZ) and nano-MoS2/Al2O3–40%YSZ (AZM) powders and coatings are prepared and studied to reveal the effect of nano-MoS2 on the friction and wear behavior of the coating. The morphology, surface roughness and hardness are observed and measured by a scanning electron microscope, a laser scanning confocal microscope and a micro-hardness tester. The ability to resist fracture of the coatings is evaluated by scratch tests. The friction and wear tests of the coatings are conducted by a ball-on-disc tribometer. The experimental results show that AZ and AZM coatings have similar morphology and roughness. But nano-MoS2 decreases the hardness and improves the ability to resist fracture of the coating. Besides, nano-MoS2 decreases the coefficients of friction of the coating when the normal loads are high. The wear rates of AZM coating decrease by 38.7%, 29.7%, 23.6% and 11% compared with those of AZ coating under normal loads of 5N, 10N, 15N and 20N. The addition of nano-MoS2 endows the coating self-lubricating function. The main wear mechanism of the coatings is micro-fracture accompanied by splat delamination and slight abrasion wear. [ABSTRACT FROM AUTHOR]

Micro-ultrasonic machining (MUSM) is an effective way of processing microstructures made from hard and brittle materials, although controlling the fluctuation of the machining force during processing is difficult. To control the quality of micro-holes fabricated in hard and brittle materials, MUSM with force control (MUSMFC) is used to study the edge chipping rate (ECR) and material removal rate (MRR) during micro-hole fabrication. The process is controlled using a force sensor and a processing control strategy. Various experiments are designed to assess the processing efficacy. Comparative experiments indicate that the ECR with MUSMFC is superior to that with traditional MUSM. Single-factor experiments show that the ultrasonic power and the fluctuation of the machining force exert a significant influence on the ECR. The influence of the spindle speed on the ECR is small. Orthogonal experiments show that the fluctuations of the machining force and ultrasonic power have large impacts on the MRR. The spindle speed has a significant impact on the MRR as well, whereas the mass fraction has little effect. The best combination of ECR and MRR is obtained using a spindle speed of 500 rpm, a machining-force fluctuation of 0.1 N, an ultrasonic power of 50 W, and a mass fraction of 10%. [ABSTRACT FROM AUTHOR]

The working mechanism of the tool electrode in grinding-aided electrochemical discharge machining (G-ECDM) of metal matrix composites process has been studied in this paper. A series of experiments have been conducted to study tool electrode clogging and damage under different processing conditions. Moreover, the grit volume fractions and average grit height of the G-ECDM tool electrode have been studied to discover the working mechanism of the tool. The experimental results have shown that in the G-ECDM situation, though it is possible for the grinding effect to cause tool clogging, the clogged materials may be removed by the polarity spark effect and thus a stable processing condition can be obtained. Moreover, the tool life of G-ECDM is much longer than that of ECDM. The reason for this phenomenon could be that the binding materials between the diamond grits of the tool surface are potentially protected by the clogged materials during the process. [ABSTRACT FROM AUTHOR]

A bimodal porous TiNi-TiNi shape memory alloy composite (SMAC) with 59% porosity was fabricated by sintering Ti-46at.%Ni elemental powders with pore-forming agent. The porous TiNi-TiNi SMAC contains two irregular pores of about 400 and 120 μm. We investigated the microstructure and pore morphology correlated with the mechanical properties and damping capacities of the SMAC. TiNi intermetallic phases with size of 1-3 μm were homogeneously distributed in the TiNi matrix. The porous TiNi-TiNi SMAC exhibits exceptionally high inverse mechanical quality factor ( Q ) of ~0.25 at < 40 °C, which is among the highest value reported for porous/dense shape memory alloys or composites to best of our knowledge, and it shows very high compressive fracture strain of about 25%. Moreover, the fabricated porous SMAC at relatively low strain amplitude can exhibit considerable high Q of 0.06 ~ 0.11 for a wide range of temperature between − 90 and 200 °C, which is attributed to the stress concentration distribution provided by the bimodal structure of pores and the massive interfaces between pore/matrix and TiNi/TiNi. These porous SMACs can be an ideal candidate for using as a lightweight damping material in the energy-saving applications. [ABSTRACT FROM AUTHOR]

A new constrained flow mode was developed to improve the machining stability in pulse electrochemical machining (PECM) of micro channel arrays on metallic bipolar plate. In electrochemical machining (ECM), the electrolyte flow field in the machining region is a key factor influencing processing stability and surface quality. In this study, a multifunctional cathode (MFC) was designed in the process, which was prepared with casting molding method. MFC acted as electrode, as well as sealing device and isolating individual machining regions. The channels of electrode were filled with elastic blocks, which were tightly pressed against the surface of workpiece during process to separate the large machining region into multiple independent machining regions. Therefore, the machining area would have sufficient electrolyte, and the flow field of each channel was independent from each other. 3-D flow field simulation was developed in this study to analyze the flow field of the channel arrays. It indicated that multiple independent machining regions could effectively improve the velocity uniformity of each channel. The experiments revealed that the uniformity of flow field had a positive role to prevent from spark discharge and short circuit, as well as the machining efficiency and machining stability. The channel arrays with 466-μm depth were machined on SS304 metallic BP within 2 min. [ABSTRACT FROM AUTHOR]

The large lead ball nut is a key component in high-speed ball screws. To solve the interference problem encountered in traditional machining of large lead ball nuts, a numerically controlled pulse electrochemical machining (NC-PECM) of large lead ball nut raceway has been proposed. This new method is capable of machining a ball nut raceway with an arbitrary lead angle, and a spherical cathode with slant jet has been designed for this process. In this paper, a detailed explanation for this process is presented, including its shaping mechanisms, and the morphology of the machined surface has also been experimentally analyzed. A large lead angle of 45° (four to five times larger than the standard of large lead angle) has been successfully machined with a raceway surface roughness of 0.54 μm Ra, and a profile accuracy of ±0.025 mm (− βc < β < βc) can be reached on the raceway. [ABSTRACT FROM AUTHOR]

Thin-film lithium-ion batteries are the most competitive power sources for various kinds of micro-electro-mechanical systems and have been extensively researched. The present paper reviews the recent progress on Sn-based thin-film anode materials, with particular emphasis on the preparation and performances of pure Sn, Sn-based alloy, and Sn-based oxide thin films. From this survey, several conclusions can be drawn concerning the properties of Sn-based thin-film anodes. Pure Sn thin films deliver high reversible capacity but very poor cyclability due to the huge volume changes that accompany lithium insertion/extraction. The cycle performance of Sn-based intermetallic thin films can be enhanced at the expense of their capacities by alloying with inactive transition metals. In contrast to anodes in which Sn is alloyed with inactive transition metals, Sn-based nanocomposite films deliver high capacity with enhanced cycle performance through the incorporation of active elements. In comparison with pure Sn anodes, Sn-based oxide thin films show greatly enhanced cyclability due to the in situ formation of Sn nanodispersoids in an LiO matrix, although there is quite a large initial irreversible capacity loss. For all of these anodes, substantial improvements have been achieved by micro-nanostructure tuning of the active materials. Based on the progress that has already been made on the relationship between the properties and microstructures of Sn-based thin-film anodes, it is believed that manipulating the multi-phase and multi-scale structures offers an important means of further improving the capacity and cyclability of Sn-based alloy thin-film anodes. [ABSTRACT FROM AUTHOR]

The crystallography of body-centered-cube to face-centered cube (bcc-to-fcc) diffusion phase transformations in a duplex stainless steel and a Cu-Zn alloy, including long axis, orientation relationship (OR), habit plane (HP), and dislocation spacing, is successfully interpreted with one-step rotation from the Bain lattice relationship by applying a simplified invariant line (IL) analysis. It is proposed that the dislocation slipping direction in the matrix plays an important role in controlling the crystallography of precipitation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to report the authors’ experience in performing adult-to-adult living donor liver transplantation (LDLT) by using a modified technique in using grafts of the right lobe of the liver. From January 2002 to September 2006, 56 adult patients underwent LDLT using right lobe grafts at the West China Hospital, Sichuan University Medical School, China. All patients underwent a modified operation designed to improve the reconstruction of the right hepatic vein (RHV) and the tributariers of the middle hepatic vein (MHV) by interposing a vessel graft, and by anastomosing the hepatic arteries and bile ducts. There were no severe complications or deaths in all donors. Fifty-two (92.8%) recipients survived the operations. Among the 56 recipients, complications were seen in 15 recipients (26.8%), including hepatic vein stricture (one case), small-for-size syndrome (one case), hepatic artery thrombosis (two cases), intestinal bleeding (one case), bile leakage (two cases), left subphrenic abscess (one case), renal failure (two cases) and pulmonary infection (five cases). Within three months after transplantation, four recipients (7.14%) died due to small-for-size syndrome (one case), renal failure (one case) and multiple organ failure (two cases). All patients underwent direct anastomoses of the RHV and the inferior vena cava (IVC), and in 23 cases, reconstruction of the right inferior hepatic vein was also done. In 24 patients, the reconstruction of the tributaries of the MHV was also done by interposing a vessel graft to provide sufficient venous outflow. Trifurcation of the portal vein was seen in nine cases. Thus, veno-plasty or separate anastomoses were performed. The graft and recipient body weight ratios (GRWR) were between 0.72% and 1.43%, and in three cases it was <0.8%. The graft weight to recipient standard liver volume ratios (GV/SLV) were between 31.86% and 71.68%, among which four cases had <40%. No “small-for-size syndrome” occurred. With modification of the surgical technique, especially in the reconstruction of the hepatic vein to provide sufficient venous outflow, living donor liver grafts in adults using the right lobe of the liver can become a relatively safe procedure and prevent the “small-for-size syndrome”. [ABSTRACT FROM AUTHOR]

The method of calculating the invariant line in HCP→BCC precipitation based on the invariant line strain model is described. The experimentally determined crystallographic features of the lath-shaped or needle-like precipitates formed in the HCP→BCC precipitations occurring in Mg−Al and Zr−Nb alloys were found to be in excellent agreement with the predictions from the model, thus suggesting that the model is valid for predicting the crystallography of diffusion-controlled phase transformations. [ABSTRACT FROM AUTHOR]

Metal atoms often locate in energetically favorite close-packed planes, leading to a relatively high penetration barrier for other atoms. Naturally, the penetration would be much easier through non-close-packed planes, i.e. high-index planes. Hydrogen penetration from surface to the bulk (or reversely) across the packed planes is the key step for hydrogen diffusion, thus influences significantly hydrogen sorption behaviors. In this paper, we report a successful synthesis of Mg films in preferential orientations with both close- and non-close-packed planes, i.e. (0001) and a mix of (0001) and (103), by controlling the magnetron sputtering conditions. Experimental investigations confirmed a remarkable decrease in the hydrogen absorption temperature in the Mg (103), down to 392 K from 592 K of the Mg film (0001), determined by the pressure-composition-isothermal (PCI) measurement. The ab initio calculations reveal that non-close-packed Mg(103) slab is advantageous for hydrogen sorption, attributing to the tilted close-packed-planes in the Mg(103) slab. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured Al2O3-40%YSZ (AZ) and nano-MoS2/Al2O3–40%YSZ (AZM) powders and coatings are prepared and studied to reveal the effect of nano-MoS2 on the friction and wear behavior of the coating. The morphology, surface roughness and hardness are observed and measured by a scanning electron microscope, a laser scanning confocal microscope and a micro-hardness tester. The ability to resist fracture of the coatings is evaluated by scratch tests. The friction and wear tests of the coatings are conducted by a ball-on-disc tribometer. The experimental results show that AZ and AZM coatings have similar morphology and roughness. But nano-MoS2 decreases the hardness and improves the ability to resist fracture of the coating. Besides, nano-MoS2 decreases the coefficients of friction of the coating when the normal loads are high. The wear rates of AZM coating decrease by 38.7%, 29.7%, 23.6% and 11% compared with those of AZ coating under normal loads of 5N, 10N, 15N and 20N. The addition of nano-MoS2 endows the coating self-lubricating function. The main wear mechanism of the coatings is micro-fracture accompanied by splat delamination and slight abrasion wear. [ABSTRACT FROM AUTHOR]