Showing papers by "Xiaojian Wang published in 2018"
TL;DR: The enhanced mechanical properties of the metals and alloys after high-density electropulsing treatment are reflected by the significant improvement of elongation, which holds great promise in improving the deformation limit and repairing cracks and defects in the plastic processing of metals.
Abstract: The technology of high-density electropulsing has been applied to increase the performance of metallic materials since the 1990s and has shown significant advantages over traditional heat treatment in many aspects. However, the microstructure changes in electropulsing treatment (EPT) metals and alloys have not been fully explored, and the effects vary significantly on different material. When high-density electrical pulses are applied to metals and alloys, the input of electric energy and thermal energy generally leads to structural rearrangements, such as dynamic recrystallization, dislocation movements and grain refinement. The enhanced mechanical properties of the metals and alloys after high-density electropulsing treatment are reflected by the significant improvement of elongation. As a result, this technology holds great promise in improving the deformation limit and repairing cracks and defects in the plastic processing of metals. This review summarizes the effect of high-density electropulsing treatment on microstructural properties and, thus, the enhancement in mechanical strength, hardness and corrosion performance of metallic materials. It is noteworthy that the change of some properties can be related to the structure state before EPT (quenched, annealed, deformed or others). The mechanisms for the microstructural evolution, grain refinement and formation of oriented microstructures of different metals and alloys are presented. Future research trends of high-density electrical pulse technology for specific metals and alloys are highlighted.
61 citations
TL;DR: In comparison to the samples without treatment, both the wear rate and the frictional coefficient of the TNZT samples with textured TiN coatings decreased significantly, and the surface dimples served as micro-hydrodynamic bearing, which were able to keep liquid inside.
Abstract: The Ti-35Nb-7Zr-5Ta (TNZT) alloy has received much research attention among the biomedical titanium alloys for its low Young's modulus and outstanding biocompatibility. This paper provided an innovative technique for improving the wear and corrosion resistance of the TNZT alloy, by developing in-situ formed TiN coatings on the surface of the TNZT alloy through laser irradiation. The new technique combines the advantages of laser surface texturing and laser gas alloying. The experimental results showed that the phase compositions of the textured TNZT samples were β-Ti, martensitic α'' phase and TiN after laser texturing in N2. The diameter of the surface dimples increased, when the width of laser pulse increased from 0.3ms to 0.7ms, and the depth decreased accordingly. In comparison to the samples without treatment, both the wear rate and the frictional coefficient of the TNZT samples with textured TiN coatings decreased significantly. The surface dimples served as micro-hydrodynamic bearing, which were able to keep liquid inside. As a result, the sample with a width of pulse of 0.3ms treated in N2 exhibited the lowest wear rate of 0.025 × 10-2m3/Nm, while the value of the sample without treatment was 0.351 × 10-2m3/Nm. The TiN contained surface coatings also exhibited higher electrochemical impedance, higher corrosion potential and lower corrosion current density.
31 citations
TL;DR: The results indicated the stress corrosion behavior of magnesium alloys was related to the average grain size of matrix and the distribution and shape of the second phase, which suppressed the adverse effect of Sr on the SCC susceptibility in high Sr–containing magnesium alloy.
Abstract: The stress corrosion cracking (SCC) properties of the bi-directional forged (BDF) Mg-4Zn-0.6Zr-xSr (ZK40-xSr, x = 0, 0.4, 0.8, 1.2, 1.6 wt %) alloys were studied by the slow strain rate tensile (SSRT) testing in modified simulated body fluid (m-SBF). The average grain size of the BDF alloys were approximately two orders of magnitude smaller than those of the as-cast alloys. However, grain refinement increased the hydrogen embrittlement effect, leading to a higher SCC susceptibility in the BDF ZK40-0/0.4Sr alloys. Apart from the grain refinements effect, the forging process also changed the distribution of second phase from the net-like shape along the grain boundary to a uniformly isolated island shape in the BDF alloys. The SCC susceptibility of the BDF ZK40-1.2/1.6Sr alloys were lower than those of the as-cast alloys. The change of distribution of the second phase suppressed the adverse effect of Sr on the SCC susceptibility in high Sr–containing magnesium alloys. The results indicated the stress corrosion behavior of magnesium alloys was related to the average grain size of matrix and the distribution and shape of the second phase.
20 citations
TL;DR: Ag-ion-modified titanium nanotube (Ag/TiO2-NT) arrays were designed and fabricated as the electrode material of supercapacitors for electrochemical energy storage and exhibited much higher electrode capacity and greatly enhanced activity in comparison to the pure TiO 2-NTs.
Abstract: Ag-ion-modified titanium nanotube (Ag/TiO2-NT) arrays were designed and fabricated as the electrode material of supercapacitors for electrochemical energy storage. TiO2 nanotube (NT) arrays were prepared by electrochemical anodic oxidation and then treated by Ag metal vapor vacuum arc (MEVVA) implantation. The Ag amount was controlled via adjusting ion implantation parameters. The morphology, crystallinity, and electrochemistry properties of as-obtained Ag/TiO2-NT electrodes were distinguished based on various characterizations. Compared with different doses of Ag/TiO2-NTs, the electrode with the dose of 5.0 × 1017 ions·cm−2 exhibited much higher electrode capacity and greatly enhanced activity in comparison to the pure TiO2-NTs. The modified electrode showed a high capacitance of 9324.6 mF·cm−3 (86.9 mF·g, 1.2 mF·cm−2), energy density of 82.8 μWh·cm−3 (0.8 μWh·g, 0.0103 μWh·cm−2), and power density of 161.0 mW·cm−3 (150.4 μW·g, 2.00 μW·cm−2) at the current density of 0.05 mA. Therefore, Ag/TiO2-NTs could act as a feasible electrode material of supercapacitors.
11 citations
TL;DR: In this article, the effect of precipitation of sigma (σ) phase on the duplex phase percentage, hardness, impact toughness and corrosion resistance of ZG0Cr26Ni5Mo3Cu3 duplex stainless steel samples treated at different tempering temperatures were observed by scanning electron microscope (SEM) and energy dispersal spectroscopy (EDS).
Abstract: ZG0Cr26Ni5Mo3Cu3 Duplex Stainless Steel (DSS) was solution treated at 1,060 oC for 3 h, followed by water cooling. Tempering treatments were conducted at 720, 750 and 780 oC, respectively, for 16 h, followed by air cooling. The microstructures of ZG0Cr26Ni5Mo3Cu3 duplex stainless steel samples treated at different tempering temperatures were observed by scanning electron microscope (SEM) and energy dispersal spectroscopy (EDS), and the phase consitutions were analyzed using X-ray diffraction (XRD). The effects of the precipitation of sigma (σ) phase on the duplex phase percentage, hardness, impact toughness and corrosion resistance of the DSS were studied. Results showed that microstructures of ZG0Cr26Ni5Mo3Cu3 after solution treatment consists of ferrite (α) phase and austenite (γ) phase; after being tempered at different temperatures, σ phase appeared due to a eutectoid-type reaction of α→σ+γ2 during tempering treatment. It was observed that σ phase distributed along the grain boundary. The volume fraction of σ and γ phases increased with increasing tempering temperature in the range of 720 to 780 oC, whereas the volume fraction of α phase showed the opposite trend. When the percentage of σ phase increased, the hardness of steel also increased. In the solution treated steel, hardness was measured to be only 244.0 HB, because σ phase did not appear. However, it increased to 391.8 HB when the DSS was tempered at 780 oC because a great of deal of σ phase appeared. The impact toughness and corrosion resistance of DSS decreased when the percentage of σ phase increased.
8 citations
Patent•
05 Jun 2018
TL;DR: In this article, a method for making a personalized degradable metal stent or an internal fixing device based on 3D printing is described. But the method is not suitable for medical applications.
Abstract: The invention discloses a method for making a personalized degradable metal stent or an internal fixing device based on 3D printing. This method includes the following steps: (1) Obtain the corresponding size parameters of the lesion in the human body through the QCA technology, and obtain the structure of the blood vessel stent, other metal stents or internal fixation devices through the three-dimensional reconstruction; (2) Build the 3D models for wax prototypes including blood vessel stents, other metal stents, or internal fixation devices in the computer, and decompose the 3D model into a series of two dimensional thin-film models; (3) Use 3D printing technology to make wax prototypes; (4) introduce plaster to the wax prototypes. After the plaster is hardened, bake it to completely evaporate the wax model prototype, and then the alloy melt is cast. After the casting is completed, the plaster shell is broken to obtain a metal stent or internal fixing device. The invention can be customized according to the patient's diseased blood vessels, and the obtained metal stent or internal fixation device is degradable, with high precision, good mechanical properties as well as good corrosion properties. Drawings Figure 1 Figure Figure 3 Page 1 of 2
2 citations