Abstract High entropy alloy is a multi-component alloy material with equal or near atomic number, which has excellent wear resistance and corrosion resistance. In this paper, AlxFeCoCrNiMn (x = 0,0.5,1.0,1.5) high entropy alloy cladding layer was prepared by laser cladding on Q345 steel plate. The phase structure, microstructure, hardness and wear resistance of the cladding layer were studied. The results show that the cladding layer of AlxFeCoCrNiMn alloy has good metallurgical bonding ability with Q345 steel. The cladding area is mainly columnar and equiaxed. The cladding layer of AlxFeCoCrNiMn alloy is mainly composed of BCC + FCC solid solution phase, which is caused by the addition of Al element under the high entropy effect. Al element promotes the formation of BCC phase structure. With the increase of Al element, the hardness of cladding layer increases. The hardness of A1.0 cladding layer is 670HV, which is close to three times of Q345 steel. When Al (x = 1.0), the hardness of the cladding layer is the highest, and it also shows better wear resistance with lower friction and wear loss.

In this paper, the multi-layer multi-pass welding process was used to weld 115mm 08Cr9W3Co3VNbCuBN (G115) steel pipe, the gas tungsten arc welding (GTAW) was used in root pass welding, subsequent welding by dynamic hot wire gas tungsten arc welding (TIP TIG) welding method, while the post-weld heat treatment (PWHT) of 770°C × 10h was carried out afterward. The microstructure and mechanical properties of different zones of the welded joint were analyzed by OM, SEM, XRD, microhardness and impact tests. The results showed that the ferrite and martensite were observed in the weld metal (WM), the fine-grained heat-affected zone (FGHAZ) and the coarse-grained heat-affected zone (CGHAZ) consisting of prior austenitic grain boundaries (PAGBs) and martensite, and more precipitates including coarse M23C6 carbides with fine MX-type carbonitrides were observed inside the grain boundaries and grains. The hardness distribution patterns along different locations (Cover, Fill, Root) on the welded joint cross-section were the same, from base metal (BM) to WM hardness gradually increased, and WM hardness was the highest. WM impact toughness was worse than HAZ, impact fracture mode was a mixed tough-brittle fracture but biased towards brittle fracture.

SUMMARY OBJECTIVE: The purpose of this study was to compare arterial stiffness and ultrasound indices in patients with and without chronic obstructive pulmonary disease. METHODS: In our retrospective study, 83 chronic obstructive pulmonary disease patients were assigned to the chronic obstructive pulmonary disease group and 80 healthy controls were enrolled. Pearson's correlation analysis software was used to analyze the correlation between arterial stiffness (including brachial ankle pulse wave velocity and ankle-brachial blood pressure index) and ultrasound index (including resistance index, pulsatility index, and intima-media thickness) at the carotid artery in chronic obstructive pulmonary disease patients. RESULTS: The ultrasound resistance index and pulsatility index level of chronic obstructive pulmonary disease group were lower than those of control group (t=6.326, 8.321, p<0.001). Compared with the control group, the chronic obstructive pulmonary disease group had higher intima-media thickness, total plaque area, and number of plaques (t=4.574, 7.493, 5.093, p<0.001). The arterial stiffness and ankle-brachial blood pressure index level in the chronic obstructive pulmonary disease group were higher than those in the control group (t=6.392, 5.109, p<0.001). Moreover, arterial stiffness in patients with chronic obstructive pulmonary disease was negatively correlated with the ankle-brachial blood pressure index, resistance index, and pulsatility index levels (p<0.05), while it is positively correlated with intima-media thickness, total plaque area, and number of plaques (p<0.05). CONCLUSION: Our results indicated that patients with chronic obstructive pulmonary disease have stiffer arteries compared with healthy control subjects; the ultrasound index could be used as an auxiliary indicator for clinical prediction of arterial stiffness, which is helpful to improve the accuracy of prediction and thus better guide clinical interventions in high-risk groups of chronic obstructive pulmonary disease in time.

Abstract In order to explore the effect of different the welding heat input on microstructure and impact properties in coarse grain zone in heat affected zone (CGHAZ) of ultra-low carbon bainitic steel welded joint. In this paper, Gleeble-3500 thermal simulation testing machine was used to simulate different heat input, to study the effect of linear energy on the microstructure and impact toughness of the CGHAZ of Q420qEN steel joint. The scanning electron microscope (SEM), oscillographic impact microscope and transmission electron microscope (TEM) were used. The results show that the microstructure of CGHAZ is mainly the lath bainite and granular bainite. When the welding heat input is 30kJ•cm-1, the CGHAZ grains have obvious growth phenomenon. With the increase of the welding heat input, the grain size also grows. Meanwhile, as the welding heat input increases from 18kJ•cm-1 to 30kJ•cm-1, the impact toughness of the CGHAZ of joint increases first and then decreases at -20°C.

Abstract The microstructure and properties of shielded metal arc welding (SMAW) joint of P91 heat-resistant steel annealed at different holding time were observed and analyzed. The results show that the martensite and residual austenite structures in the weld zone and coarse grain heat affected zone (CGHAZ) were transformed with the extension of holding time. After 760°C+4h annealing, a large number of white rod-shaped precipitates appeared in the weld zone. The main components of precipitates were Fe, Cr, Mn, V, Si, and a small amount of oxides appeared. After 760°C+5h annealing treatment, relatively fine white granular precipitation appeared in the weld zone, and a large number of oxides and some precipitates have been dissolved. After 760°C+6h annealing treatment, the precipitated phases were composed of Fe-Cr, Fe3Si, Ni-Cr-Fe, Fe2MnAl. Compared with the annealing treatment for 5h, the microstructure of the precipitated phase is fine and uniform, dispersion distribution of second phase particles, and the material mechanics is relatively stable.

Anstract Selective Laser Melting (SLM) is one of additive manufacturing techniques which enable to build a complex structure model layer by layer with 3D CAD software. However, a higher research cost makes it hardly carry out by a traditional methodology, the best way to solve the problem is using simulation software. This paper aims to find an optimal processing parameters combination for a specimen with the smallest distortion and lowest residual stress through Simufact Additive (SA) software. Simulation results under an optimal processing parameters, which led to a smallest value of distortion and residual stress, was the combination of scan power with 300W, scan speed with 1.3m/s, scan interval with one spot diameter (0.12mm) and heat treatment holding time with 4h. In addition, the calculation results provide a novel study method to verify the influence of different processing parameters on Inconel 718 alloys fabricated by SLM.

Abstract The mechanical properties and corrosion performance of the N10276 alloy welded joint were investigated with nano-hardness testing and electrochemical measurement. The results showed that solidification mode changes from equiaxed crystal to columnar crystal from the center of the weldment to the fusion zone. With the increase of immersion times, the diameter of capacitance arc and the impedance modulus increase, and the corrosion resistance of HAZ decreases. The strengthening effect of welded metal was more obvious than that of heat affected zone for the nickel-based welded joint and especially in coarse grained heat affected zone, the hardening resulted from overheating was not apparent. Nickel-based weld metal with high content of alloying elements were often segregated at interdendritic regions or precipitated in grain interior under nonequilibrium solidification, which differ from conventional low alloy steel welded joint.

Abstract Micro-arc oxidation (MAO) treatment with various voltages was carried out on Ti alloys in 10% H2SO4 aqueous solution to enhance surface wettability for biological application. The effects of applied voltage on the surface morphology, phase constituents, functional group, roughness and wettability of the MAO coatings were investigated comprehensively. Increasing applied voltages significantly change phase constituents, surface morphology and wettability of the MAO coatings. Higher applied voltages are favorable to form higher fraction of rutile phase, larger micro-pores and higher surface roughness. The apparent contact angle decreases slightly after treated at 80 V but it decreases sharply after treated at 160 V or 200 V. The significant change in wettability of MAO coatings is attributed to hydroxyl group content and morphology of the MAO coatings. Differences in hydroxyl group content and surface morphology result in different contact interface types between water and MAO coatings, which is attributed to air captured or no air captured interface models.

Influence of solid solution temperature on microstructures and corrosion properties of CoNiCrMo alloy were investigated by means of optical microscopy (OM), scanning electron microscope (SEM) and electronic differential system. The corrosion resistance of CoNiCrMo alloy in 0.9%NaCl aqueous solution was also investigated. The results indicated that with the increase of solution treatment temperature, the dendrites of CoNiCrMo alloy gradually disappeared. Thus, the corrosion resistance of the alloy decreased. When the solution temperature is 1200ºC, the dendrites almost disappeared and most carbide dissolved, and begins to spheroidization. The corrosion resistance of CoNiCrMo alloy treated at 1000ºC for 1h is the highest than the one at 1100 ºC and 1200ºC. Its self-corrosion potential is -424mV and self-corrosion current density is 1.02×10-8A/cm2.

Left atrial diameter (LAD) has been considered an independent risk factor for atrial fibrillation (AF) relapse after pulmonary vein isolation (PVI). However, whether LAD or other factors are more predictive of late recurrence in patients with paroxysmal AF remains unclear. We aimed to evaluate the value of pulmonary vein (PV) parameters for predicting AF relapse 1 year after patients underwent cryoablation for paroxysmal AF. Ninety-seven patients with paroxysmal AF who underwent PVI successfully were included. PV parameters were measured through computed tomography scans prior to PVI. A total of 28 patients had recurrence of AF at one-year follow-up. The impact of several variables on recurrence was evaluated in multivariate analyses. LAD and the time from first diagnosis of AF to ablation maintained its significance in predicting the relapse of AF after relevant adjustments in multivariate analysis. When major diameter of right inferior pulmonary vein (RIPV) (net reclassification improvement (NRI) 0.179, CI=0.031–0.326, P<0.05) and cross-sectional area (CSA) of RIPV (NRI: 0.122, CI=0.004–0.240, P<0.05) entered the AF risk model separately, the added predictive capacity was large. The accuracy of the two parameters in predicting recurrence of AF were not inferior (AUC: 0.665 and 0.659, respectively) to echocardiographic LAD (AUC: 0.663). The inclusion of either RIPV major diameter or CSA of RIPV in the model increased the C-index (0.766 and 0.758, respectively). We concluded that major diameter of RIPV had predictive capacity similar to or even better than that of LAD for predicting AF relapse after cryoablation PVI.

Microstructural evolution, interfacial reaction and fracture during vacuum brazing of 50Mo-50Re alloys using amorphous alloy Fe-5.6Si-2.6B(wt%) were investigated. A binary intermetallic compound, σ(Mo2Re3) formed as parallel contiguous layers in the diffusion zone. In addition, Fe from the braze alloy, in combination with dissolved Mo from the substrate, formed two layers of binary compounds µ-Mo6Fe7 and λ-MoFe2, adjacent to diffusion zone. The unreacted Fe-based filler metal solidified as α-Fe solid solution. Fracture analysis showed that the mode of failure was mainly transgranular cleavage with partly intergranular and the fracture located on the interface of 50Mo-50Re alloy and the central area of brazing seam.

Abstract Purpose: To investigated the effects of ginsenoside Rb1 on diabetic retinopathy in streptozotocin-induced diabetic rats. Methods: Diabetes was induced by a single intraperitoneal injection of streptozotocin (80 mg/kg) in male Wistar rats. Ginsenoside Rb1 (20, 40 mg/kg) was injected (i.p.) once a day for 4 weeks. Then, using fundus photography, the diameter and vascular permeability of retinal vessels were investigated. Retinal histopathology was undertaken. Contents of malondialdehyde (MDA) and glutathione (GSH) in retinas were assayed. Levels of nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione cysteine ligase catalytic subunit (GCLC), and glutathione cysteine ligase modulatory subunit (GCLM) were measured. Results: Treatment with ginsenoside Rb1 attenuated the diabetes-induced increase in the diameter of retinal blood vessels. Ginsenoside Rb1 reduced extravasation of Evans Blue dye from retinal blood vessels. Ginsenoside Rb1 partially inhibited the increase in MDA content and decrease in GSH level in rat retinas. Nrf2 levels in the nuclei of retinal cells and expression of GCLC and GCLM were increased significantly in rats treated with ginsenoside Rb1. Conclusion: These findings suggest that ginsenoside Rb1 can attenuate diabetic retinopathy by regulating the antioxidative function in rat retinas.

Three dimensional (3D) printing technology has been widely used in metal manufacturing industry. This study focused on the vacuum brazing of 3D printed Inconel 718 superalloy with BNi-2 amorphous filler metal. Interfacial microstructure and element distribution revealed excellent wettability and spreadability of the filler metal as well as favorable brazability of the base material. Brazed joint could be divided into two distinct zones: isothermally solidified zone (ISZ) consisting of γ-Ni solid solution and diffusion-affected zone (DAZ) consisting of a large amount of precipitates besides γ-Ni solid solution. Microhardness reached peak values in DAZ. Although borides filled the gaps of base material’s grains to restrict grain boundary sliding and restrain the expansion of gaps, but its high hardness and brittleness would cause DAZ turn into weaker region when external loads were very large. The complete diffusion of B indicated the completion of isothermally solidified process. Precipitate CrB2 with high hardness and brittleness was the key point of reducing the joint strength. Shear strength of the brazed joint was up to 802 MPa, and fracture morphology presented a mixed ductile-brittle fracture.

The microstructure in the Z-Y surface of Inconel 718 alloys fabricated by selective laser melting (SLM) shows the relatively homogeneous and irregular fine grain structure after the heat treatment process of 1050ºC solid solution + double ageing. A large number of bulk precipitates were observed on the grain boundary, and the typical dendritic crystallization and Laves phases disappeared. It is possible that a large number of δ phases (NbNi3) were precipitated on the grain boundary since the enrichment effect of element Nb. The hardness in the Z-Y surface increased from 350HV to 500HV, and the residual stress was transformed from the tensile stress to compressive stress.