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In this study, the joining experiment of SiCp/Al composites with 4 mm thickness was carried out, and the effects of different tool rotational speeds (600, 1000 and 1400 rpm) on the microstructure evolution and mechanical properties of joint were studied. The results show that the rotation speed has a significant impact on the microstructure of the weld nugget (WN). The aluminium matrix forms a fine equiaxed crystal structure in WN. As the rise of the rotational speed from 600 to 1400 rpm, the grain size of WN decreased from 6.9 to 2.3 μm. Compared with the base material, the microhardness of the nugget zone was higher. As the rise of rotational speed, the maximum microhardness value increased. The ultimate tensile strength (UTS) of joints decreased with the increase of rotational speed and can reach 95.9% of the base material at 600 rpm. The failure modes of friction stir welding (FSW) joints are mainly ductile failure and SiC particle fracture. [ABSTRACT FROM AUTHOR]

Graphene oxide particles (GOp) were implanted on the surface of H62 copper alloy by friction stir surface processing (FSSP) to obtain a H62/GOp modified layer. The recrystallization microstructure, friction, and wear property, and hardness of the modified layer were studied and analyzed. The results show that the GOp has a good dispersion in the copper matrix without obvious aggregation. The recrystallization on the layer of the modified copper alloy resulted in obvious grain refinement. When the rotating speed of the tool was 900 rpm, and the feed speed of the tool was 200 mm/min, the highest hardness value and wear resistance of the modified layer samples were obtained. The hardness value was 25.2% higher than that of the base metal. The average friction coefficient was 39.5% lower than that of the base metal. When the tool rotating speed was 1300 rpm, and the tool feed speed was 160 mm/min, the hardness value and wear resistance of the modified layer were relatively low. The hardness value was approximately 4% higher than that of the base metal. The average friction coefficient was 15.8% less than that of the base metal. The hardness and wear resistance of the modified layer were better than those of the base material under various parameters of FSSP. [ABSTRACT FROM AUTHOR]

The present research envisaged the performance analysis of a 1-mm thick 6061-T6 aluminum alloy sheet welded by the friction stir welding technique, using optical microscopy, micro-hardness measurement, a tensile test, a friction and wear test, and a salt spray corrosion test. It was found that the grain in the welded zone obtained was refined under each parameter. When the rotating speed of the tool was 15,000 rpm and the traveling speed of the tool was 300 mm·min-1, the tensile strength of the welded zone was highest, i.e. 74.8% of the base metal. Furthermore, the hardness distribution curve of the welded zone was of the 'W' type under each parameter, but the hardness value was lower than that of the base metal. The friction coefficient of the welded zone was lower than that of the base metal under each parameter, and the wear form was found to be mainly adhesive wear accompanied by abrasive wear. The welded zone and the base metal were subjected to salt spray corrosion after 12 hours under each parameter, which had a negative effect on the quality. However, after 12 hours of subsequent corrosion, the quality of each sample and the base material was not obvious. [ABSTRACT FROM AUTHOR]

The composition of intermetallic compounds and mechanical properties during friction stir welding of 2024 aluminum and AZ31B magnesium alloys was investigated by using offset tool at low heat input. The macrostructure of the Mg/Al joints was investigated by optical microscope, and microstructure characteristics were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. The fracture section was also observed. It is found that the mechanical strength of the joint slowly decreases as the value of tool offset increases first and then decreases at the Al-side. The result showed that the joints have the best mechanical properties when offset 0.5 mm and the amount of IMCs is low. And it is found that only IMCs Al12Mg17 is found in the joints. Since Al3Mg2 and Al12Mg17 have eutectic temperatures of 450 °C and 437 °C, respectively, the offset caused the temperature to decrease during the FSW process, allowing Al12Mg17, with a lower eutectic temperature, to form easily. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (cBN) films were prepared by Anode Layer Linear Ion Source (ALLIS) assisted Radio Frequency Magnetron Sputtering (RFMS) method, and the effect of deposition temperature and substrate bias voltage on the phase component, surface morphology and nanohardness was investigated. In the experiment, the critical deposition temperature of 700 °C and bias voltage of −200 V were obtained as the threshold for the formation of cBN. The cBN content in the film increased with the increase of deposition temperature, while it gradually decreased when the bias voltage exceeded −210 V. Finally, cBN films were deposited at 900 °C and −210 V with varying ALLIS power, and the residual stress in the as-deposited films was calculated. The result indicated that cBN films with low residual stress can be obtained with ALLIS at high temperature and appropriate bias voltage. [ABSTRACT FROM AUTHOR]

The chemical activation pretreatment was executed on the WC powder and the WC-Y 2 O 3 composite powder was prepared by the chemical liquid mixing method. The binderless tungsten carbide with varied amounts of Y 2 O 3 (0–4 wt%) was produced by spark plasma sintering (SPS) at 1400–1700 °C with an applied pressure of 45 MPa. The effects of Y 2 O 3 addition and the sintering temperature on the densification, microstructure and mechanical properties of the sintered sample were investigated. The results demonstrated that the addition of Y 2 O 3 was of significant influence on the sintering densification and mechanical properties of the binderless tungsten carbide. When the sintering temperature and sintering pressure were 1600 °C and 45 MPa respectively, the Vickers hardness and the fracture toughness of the WC-1 wt% Y 2 O 3 increased by 46% and 40% compared to the pure WC binderless tungsten carbide. As the Y 2 O 3 content increased further, the fracture toughness displayed a slight increase, whereas the Vickers hardness decreased highly. The sub carbide phase W 2 C was observed when the Y 2 O 3 content exceeded 2 wt% and increased with the increase of the Y 2 O 3 content. Abnormal grain growth occurred when the Y 2 O 3 content was 4 wt%. As the sintering temperature increased from 1400 °C to 1600 °C, the relative density and mechanical properties of the WC-1 wt% Y 2 O 3 increased remarkably. When the sintering temperature was 1600 °C, the binderless tungsten carbide WC-1 wt%Y 2 O 3 was obtained with the relative density of 99.7%, the Vickers hardness value of 2420 kg·mm − 2 and the fracture toughness of 10.5 MPa·m 1/2 . When the sintering temperature was further increased to 1700 °C, the sub-carbide W 2 C was formed and the fracture toughness apparently decreased. [ABSTRACT FROM AUTHOR]

Shell diamond film prepared using DC plasma jet CVD (DCPJCVD) is studied by those techniques. The relationships between morphology, microstructure, and the quality of diamond film are investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy, respectively. The results show that, high nucleation density was attained when molybdenum substrate was polished by different size diamond powder and was etched by atom hydrogen. Diamond film grows in the columnar way, and the microstructure of diamond film is compact, continuous, and uniform. (111) faces were dominant in polycrystalline texture diamond film. Raman spectrum indicates that there is only diamond characteristic peak in shell diamond film, furthermore, the velocity, pressure, and temperature fields of reaction chamber were simulated by finite element methods, which help to prepare high-quality shell diamond film. It also shown that although velocity and pressure fields fluctuated, which caused negative influence on the quality of diamond film, the temperature field is uniform, which is very important to grow normal diamond film, and it is in accordance with the experience results. [ABSTRACT FROM PUBLISHER]

Shell diamond film prepared using DC plasma jet CVD (DCPJCVD) is characterized by those techniques. The relationships between morphology, microstructure, and film quality are investigated by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy, respectively. The results show that, after molybdenum substrate was polished by series of diamond powder, atom hydrogen etching, a much higher nucleation density can be achieved. Synthetic diamond film is compact, continuous and uniform, and diamond film grows with the columnar spreading from the nucleation surface to the growth surface. (111) Faces were dominant in polycrystalline texture diamond film. Raman spectrum indicates that there is only diamond characteristic peak in diamond film; furthermore, the velocity, pressure, and temperature fields of reaction chamber were simulated by finite element methods respectively, which is help to prepare high quality shell diamond film. It also showed that, though uneven velocity and pressure fields' distributions have negative influence on the growth of diamond film, the temperature field is uniform, which guarantees to grow normally diamond film, and it accords with the experience results. [ABSTRACT FROM AUTHOR]

Research on pre-deformation influences on material properties in multistep hot forming is of important scientific interest. In this paper, hot tensile tests at 850 °C and a strain rate of 0.001 s−1 were performed to study the microstructural evolution and mechanical properties of Ti-6Al-4V with pre-strains at 0.05, 0.1 and 0.15. The tensile test results showed that the specimen with 0.05 pre-strain exhibited higher flow stress and larger elongation. Additionally, increasing the pre-strain resulted in a decrease in ultimate tensile strength (UTS) and elongation (EL). The EBSD results showed that the main deformation mechanism of Ti-6Al-4V was high-angle grain boundary sliding. Pre-strain promoted dynamic recrystallization (DRX) by increasing the deformation substructure. The refinement of grains and the eradication of dislocations enhanced the deformability, resulting in an increase in flow stress. [ABSTRACT FROM AUTHOR]

To improve the longevity of medical devices in physiological environments, a series of TiZrNbTaMoC x N y coatings were fabricated on 316L stainless steel using RF magnetron sputtering. The work demonstrated that appropriate carbon doping can effectively enhance the density, electrochemical properties, and resistance to tribo-corrosion of the coatings. Among the tested samples, coating S4 with a carbon content of 24 at. % exhibited the lowest wear rate (6.496 × 10−7 mm3 N−1 m−1) during the tribo-corrosion tests, due to its favorable lubrication characteristic (COF = 0.127) and enhanced resistance to plastic deformation (H3/E2 = 0.78 Gpa). Additionally, coating S5 with a carbon content of 28 at. % showed superior electrochemical performance (i c o r r = 5.21 × 10−8 A), attributed to its higher coating density and ability to form passive films. Both S4 and S5 exhibited superior biocompatibility compared to 316L. [Display omitted] [ABSTRACT FROM AUTHOR]

Anode Layer Linear Ion Source (ALLIS) can improve the ionization rate of working gases and enhance the activity of gas molecules. In the present work, the ALLIS assisted Radio Frequency Magnetron Sputtering (RFMS) method was proposed to deposit cubic boron nitride (cBN) films, and the effect of ALLIS on the microstructure and mechanical properties of the deposited cBN films was investigated. The phase component, chemical composition, bonding states, surface topography, deposition rate and nanohardness of the cBN films were characterized respectively by Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and nanoindentation. The results indicated that the sp 3 phase content in cBN films increased at first and then decreased with the increase of ALLIS power, and the maximum value was 83% when the ALLIS power was 200 W, the surface quality and growth rate of cBN films were enhanced markedly. The hardness and elastic modulus exhibited the same trend to variation of cubic phase content. Finally, the effect of ALLIS on the cBN synthesis was discussed systematically. [ABSTRACT FROM AUTHOR]

In order to study the effects of anode layer linear ion source(ALLIS)on the microstructure and mechanical properties of amorphous carbon nitride ( a -CN x ) films, a -CN x films were deposited by the ALLIS assisted radio frequency magnetron sputtering (RFMS) deposition condition changing the ion source power from 0 to 200 W. The growth rate, structural morphology, surface roughness, nanohardness as well as the bonding states of deposited a -CN x films were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), nanoindentation, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. The H / E and hardness increased relatively with increasing the ion source power up to 100 W. From the Micro Raman analysis, the content of sp 3 carbon in sp 3 /sp 2 ratio was increased with increasing the ion source power. The cross-sectional SEM images demonstrated that the ion source enhanced the growth rate of a -CN x films. Meanwhile, the roughness was increased with the ion source power above 100 W. Therefore, the optimum ion source power is considered to be around 100 W in these experimental conditions. [ABSTRACT FROM AUTHOR]