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Shen J.,Chongqing University | Wen L.,Chongqing University | Luo X.,Chongqing University | Xu N.,Chongqing University | And 3 more authors.
Science and Technology of Welding and Joining | Year: 2014

In this work, a new heating tool friction stir spot welding (HT-FSSW) process was developed, and its impacts on the microstructure and mechanical properties of the welded AZ31 magnesium alloy joints were investigated by microstructure observation, tensile tests and microhardness tests. An increase in the heating tool temperature resulted in a decrease in the grain size of the stir zone (SZ) and an increase in the grain size of the thermomechanically affected zone (TMAZ). The rising heating tool temperature also aggrandised the bonded zone width and enhanced the tensile shear load strength per unit area of the HT-FSSW welded joints. With an increase in the heating tool temperature, the microhardness of SZ increased while that of the TMAZ decreased. Moreover, the slope of the Hall-Petch relationship between microhardness and grain size of the TMAZ is larger than that of the SZ. © 2014 Institute of Materials, Minerals and Mining. Source


Shen J.,Chongqing University | Pu Y.,Chongqing University | Yin H.,Chongqing University | Luo D.,Eunow Company Ltd | And 2 more authors.
Journal of Alloys and Compounds | Year: 2014

The effects of Cu and Zn additions on microstructures, thermal and mechanical properties of Sn-Bi-based solder alloy were investigated. Thermal analysis indicated that Cu addition decreased both melting point and paste region of Sn-Bi-based solder while Zn played a reverse effect. Alloying Cu into binary solder resulted in an increase in both ultimate tensile strength and ductility. The improved strength of the Sn-40Bi-0.1Cu solder was attributed to the microstructural refinement and uniform distribution of the Cu 6Sn5 intermetallic particles. The addition of Zn further depressed the precipitation of Bi, formed uniform globular CuZn2 particles as well as flat blocky Cu5Zn8 phase. The enhanced strength of Zn-containing solder was ascribed to the presence of the globular CuZn2 particles and structural refinement. Needle-like Zn with high aspect ratio forms at the position around the Bi-rich phase and leads a significant decrease of the elongation of Sn-40Bi-2Zn-0.1Cu solder. Fracture surface analysis indicated that the addition of Cu and Zn in Sn-Bi-based solder alloy did not affect the mode of fracture, and all tested solder exhibited brittle fracture with a pattern mixing with tongue and cleavage on the fracture surface. © 2014 Elsevier B.V. All rights reserved. Source


Mo Y.,Chongqing Materials Research Institute Co. | Mo Y.,National Engineering Research Center for Instrument Functional Materials | Mo Y.,Chongqing University | Wang D.-Z.,Chongqing Materials Research Institute Co. | And 14 more authors.
Materials Science Forum | Year: 2016

With the application upgrade of alloy 718 in the marine oil exploitation, higher corrosion resistance demands has been presented for structure design and reasonable material application of drilling and production equipments; thus there is an urgent need to understand influences of grain size on corrosion behavior of such alloy in sea water environment. In this experiment, different solution treatments are applied to nickel-based alloy 718. As a result, specimens with grain size varied from ASTM No. 9 to No. 3.5 grades. The influences of grain size on the electrochemical behaviors in simulated sea water (3.5% sodium chloride solution) are investigated using electrochemical impedance spectroscopy and polarization curves. Alloy 718 shows good corrosion resistance in this electrolyte solution, however, grain size still has an effect on its electrochemical corrosion behaviors to a certain extent. With the time going, testing results show that coarse-grained alloys with larger grain size have higher impedance values and smaller corrosion current densities, indicating a better corrosion resistance than fine-grained specimens. However, when the grain size increases further, the corrosivity resistant nature of alloy 718 would decline. Testing results show that specimen with size of ASTM No. 5 has the best corrosion resistance. © 2016 Trans Tech Publications, Switzerland. Source


Zou X.Z.,Chongqing Materials Research Institute Co. | Ge S.P.,Chongqing University of Technology | Wang H.,Chongqing Materials Research Institute Co. | Li F.,Chongqing Materials Research Institute Co. | And 4 more authors.
Advanced Materials Research | Year: 2014

The biocompatibility of the austenitic stainless steel with different nitrogen contents was studied, The MTT(3-(4,5-Dimethylthi azol-2-yl)-2,5-diphenyltetra zolium bromide) assay, platelet adhesion and hemolysis rate test were used to examine the cytotoxicity. The cell compatibility of materials was investigated by cell adhesion test. Hemolysis rate test and platelet adhesion were used to examine the blood compatibility. The cell toxicity test showed that the nickel free austenitic stainless steel materials of different nitrogen content and the control group of titanium alloy materials had no significant side effects for vascular endothelial cells. The cell adhesion test showed that the cell number of vascular endothelial in the austenitic stainless steel was more than the titanium alloy materials, and the cells grow in good condition. The hemolysis rate was lower than 5%, and the influence of platelet was not significant, and pyrogen test results can be considered that such material extracts heat checking compliance with safety regulations. © (2014) Trans Tech Publications, Switzerland. Source


Liu W.,Hunan University | Liu W.,Chongqing Materials Research Institute Co. | Wang D.,Chongqing Materials Research Institute Co. | Chen X.,Hunan University | And 2 more authors.
Corrosion Engineering Science and Technology | Year: 2016

Sulphur corrosion for nickel alloy 718 was monitored by electrochemical noise under high temperature. Cross-recurrence quantification analysis (CRQA) on potential and current noise signals was used to characterise the stable coupling interaction between them. Diagnosis criterion for stable pitting started was proposed based on the CRQA parameter determinism per cent trajectory. The proposed method displayed accurate and robust characteristics compared to the common localisation index. © 2015 Institute of Materials, Minerals and Mining Source

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