The effect of welding speed on tensile and microstructural characteristics of pulsed current gas tungsten arc welded（PCGTAW） AZ31 B magnesium alloy joints was studied. Five joints were fabricated using different lev...The effect of welding speed on tensile and microstructural characteristics of pulsed current gas tungsten arc welded（PCGTAW） AZ31 B magnesium alloy joints was studied. Five joints were fabricated using different levels of welding speeds（105-145 mm/min）. It was found that the joints fabricated using a welding speed of 135 mm/min yielded superior tensile properties compared to other joints. The formation of fine grains and uniformly distributed precipitates in the fusion zone are the main reasons for the superior tensile properties of these joints.展开更多
The reaction behaviors of silicate species in （NH4）2WO4-（NH4）2CO3-NH3-H2O system are crucial to developing a greenmanufacture technique for ammonium paratungstate. In order to efficiently remove silicon from the s...The reaction behaviors of silicate species in （NH4）2WO4-（NH4）2CO3-NH3-H2O system are crucial to developing a greenmanufacture technique for ammonium paratungstate. In order to efficiently remove silicon from the system, the reaction behaviors ofsilicate species were systematically investigated by thermodynamic analysis. The thermodynamic analysis shows that silicate in thetungstate clinker partly decomposes in the leaching process, with 150-160 mg/L silicon thermodynamically at 25 ℃. The dissolvedsilicon can be removed by magnesium salts via forming insoluble MgSiO3. The low carbonate and high ammonia concentrations inthe system are beneficial to the removal of silicon, with silicon concentration reaching 8-10 mg/L thermodynamically, whereasMgSiO3 precipitation is hardly formed when the concentration of total carbonate is more than 1.5 mol/L. The reaction behaviors ofcalcium and magnesium were also studied in the system. The results in the verification experiments consist with the theoreticalcalculation.展开更多
The effects of Sn addition on the microstructure and mechanical properties of gas tungsten arc butt-welded Mg?6Al?0.3Mn (AM60) (mass fraction, %) alloy sheets were investigated by optical microscopy, scanning electron...The effects of Sn addition on the microstructure and mechanical properties of gas tungsten arc butt-welded Mg?6Al?0.3Mn (AM60) (mass fraction, %) alloy sheets were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and microhardness and tensile tests. The results indicate that both the average microhardness and joint efficiency of AM60 are improved by the addition of 1% Sn (mass fraction). The ultimate tensile strength of Mg?6Al?1Sn?0.3Mn (ATM610) reaches up to 96.8% of that of base material. Moreover, fracture occurs in the fusion zone ofATM610 instead of in the heat-affected zone of AM60 welded joint. The improvement in the properties is mainly attributed to the formation of Mg2Sn, which effectively obstructs the grain coarsening in the heat-affected zone, resulting in a relatively finemicrostructure. The addition of 1% Sn improves the mechanical properties of AM60 welded joint展开更多
An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency...An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.展开更多
Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate.The effects of sodium tungstat...Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate.The effects of sodium tungstate on the coating thickness, mass gain,surface morphology and corrosion resistance were studied by eddy current instrument,electronic scales,scanning electron microscope and immersion tester.With the addition of sodium tungstate,the electrolytic conductivity increases and the final voltage decreases.The sodium tungstate has a minor effect on the coating thickness,but lightens the coating color.With increasing sodium tungstate concentration,the size of micropores on the coatings is enlarged and the corrosion resistance of the anodized samples decreases.展开更多
The effects of graphene nanoplates(GNPs)on the microstructures and mechanical properties of nanoparticlesstrengthening activating tungsten inert gas arc welding(NSA-TIG)welded AZ31magnesium alloy joints were investiga...The effects of graphene nanoplates(GNPs)on the microstructures and mechanical properties of nanoparticlesstrengthening activating tungsten inert gas arc welding(NSA-TIG)welded AZ31magnesium alloy joints were investigated.It wasfound that compared with those of activating TIG(A-TIG),and obvious refinement ofα-Mg grains was achieved and the finestα-Mggrains of fusion zone of NSA-TIG joints were obtained in the welded joints with TiO2+GNPs flux coating.In addition,thepenetrations of joints coated by TiO2+GNPs flux were similar to those coated by the TiO2+SiCp flux.However,the welded jointswith TiO2+GNPs flux coating showed better mechanical properties(i.e.,ultimate tensile strength and microhardness)than those withTiO2+SiCp flux coating.Moreover,the generation of necking only occurred in the welded joints with TiO2+GNPs flux.展开更多
采用固相烧结法制备了(W0.5Mg0.5)^4+复合离子掺杂的(Bi0.5Na0.5)0.94Ba0.06Ti1-x(W0.5Mg0.5)xO3(BNBT-x WM)无铅陶瓷,研究了(W0.5Mg0.5)^4+复合离子掺杂量对BNBT陶瓷的表面形貌、微观结构,以及铁电、应变、压电、介电等电学性能的影响...采用固相烧结法制备了(W0.5Mg0.5)^4+复合离子掺杂的(Bi0.5Na0.5)0.94Ba0.06Ti1-x(W0.5Mg0.5)xO3(BNBT-x WM)无铅陶瓷,研究了(W0.5Mg0.5)^4+复合离子掺杂量对BNBT陶瓷的表面形貌、微观结构,以及铁电、应变、压电、介电等电学性能的影响。结果表明:(W0.5Mg0.5)^4+复合离子进入了BNBT陶瓷的B位并形成了单一的钙钛矿结构,且陶瓷样品晶界清晰,结构致密。(W0.5Mg0.5)^4+掺杂增大了剩余极化强度和饱和极化强度。(W0.5Mg0.5)^4+复合离子的掺杂使电致应变曲线由蝴蝶形变为嫩芽形,在x=0.03时获得0.429%(质量分数)的高电致应变响应,d33*的最大值为833.1 pm/V,其外加高场仅有60 k V/cm。在x=0.02时其低场小信号的压电性能d33有235 p C/N。BNBT-x WM陶瓷的介电常数随着掺杂含量的增多逐渐降低且平坦化,同时向弛豫铁电体转变。展开更多
基金University Grant Commission (UGC), New Delhi for financial support rendered through Major Research Project No: 39-864/2010
文摘The effect of welding speed on tensile and microstructural characteristics of pulsed current gas tungsten arc welded（PCGTAW） AZ31 B magnesium alloy joints was studied. Five joints were fabricated using different levels of welding speeds（105-145 mm/min）. It was found that the joints fabricated using a welding speed of 135 mm/min yielded superior tensile properties compared to other joints. The formation of fine grains and uniformly distributed precipitates in the fusion zone are the main reasons for the superior tensile properties of these joints.
基金Project(51274243)supported by the National Natural Science Foundation of ChinaProject(2015CX001)supported by the Innovation-driven Plan of Central South University,China
文摘The reaction behaviors of silicate species in （NH4）2WO4-（NH4）2CO3-NH3-H2O system are crucial to developing a greenmanufacture technique for ammonium paratungstate. In order to efficiently remove silicon from the system, the reaction behaviors ofsilicate species were systematically investigated by thermodynamic analysis. The thermodynamic analysis shows that silicate in thetungstate clinker partly decomposes in the leaching process, with 150-160 mg/L silicon thermodynamically at 25 ℃. The dissolvedsilicon can be removed by magnesium salts via forming insoluble MgSiO3. The low carbonate and high ammonia concentrations inthe system are beneficial to the removal of silicon, with silicon concentration reaching 8-10 mg/L thermodynamically, whereasMgSiO3 precipitation is hardly formed when the concentration of total carbonate is more than 1.5 mol/L. The reaction behaviors ofcalcium and magnesium were also studied in the system. The results in the verification experiments consist with the theoreticalcalculation.
基金Project(51474043)supported by the National Natural Science Foundation of ChinaProject(2014DFG52810)supported by the Ministry of Science and Technology of China+2 种基金Projects(SRFDR 20130191110018,CDJZR13130086)supported by the Ministry of Education of ChinaProject(CSTC2013JCYJC60001)supported by the Chongqing Municipal Government,ChinaProjects(CSTC2012gg B50003,CSTC2013jj B50006)supported by the Natural Science Foundation of Chongqing Science and Technology Commission,China
文摘The effects of Sn addition on the microstructure and mechanical properties of gas tungsten arc butt-welded Mg?6Al?0.3Mn (AM60) (mass fraction, %) alloy sheets were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and microhardness and tensile tests. The results indicate that both the average microhardness and joint efficiency of AM60 are improved by the addition of 1% Sn (mass fraction). The ultimate tensile strength of Mg?6Al?1Sn?0.3Mn (ATM610) reaches up to 96.8% of that of base material. Moreover, fracture occurs in the fusion zone ofATM610 instead of in the heat-affected zone of AM60 welded joint. The improvement in the properties is mainly attributed to the formation of Mg2Sn, which effectively obstructs the grain coarsening in the heat-affected zone, resulting in a relatively finemicrostructure. The addition of 1% Sn improves the mechanical properties of AM60 welded joint
文摘An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.
基金Projects(GJJ08363,GJJ09573)supported by the Scientific Research Fund of Jiangxi Provincial Education Department,China
文摘Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate.The effects of sodium tungstate on the coating thickness, mass gain,surface morphology and corrosion resistance were studied by eddy current instrument,electronic scales,scanning electron microscope and immersion tester.With the addition of sodium tungstate,the electrolytic conductivity increases and the final voltage decreases.The sodium tungstate has a minor effect on the coating thickness,but lightens the coating color.With increasing sodium tungstate concentration,the size of micropores on the coatings is enlarged and the corrosion resistance of the anodized samples decreases.
基金Project(51375511) supported by the National Natural Science Foundation of ChinaProject(cstc2016jcyj A0167) supported by the Research Program of Basic Research and Frontier Technology of Chongqing of China+1 种基金Project(SF201602) supported by the Science and Technology Project in the Field of Social Development of Shapingba District of Chongqing of ChinaProject(XJ201608) supported by the Key Industry Technology Innovation Funds of Science and Technology Development Board of Xiangcheng District of Suzhou of China
文摘The effects of graphene nanoplates(GNPs)on the microstructures and mechanical properties of nanoparticlesstrengthening activating tungsten inert gas arc welding(NSA-TIG)welded AZ31magnesium alloy joints were investigated.It wasfound that compared with those of activating TIG(A-TIG),and obvious refinement ofα-Mg grains was achieved and the finestα-Mggrains of fusion zone of NSA-TIG joints were obtained in the welded joints with TiO2+GNPs flux coating.In addition,thepenetrations of joints coated by TiO2+GNPs flux were similar to those coated by the TiO2+SiCp flux.However,the welded jointswith TiO2+GNPs flux coating showed better mechanical properties(i.e.,ultimate tensile strength and microhardness)than those withTiO2+SiCp flux coating.Moreover,the generation of necking only occurred in the welded joints with TiO2+GNPs flux.
文摘采用固相烧结法制备了(W0.5Mg0.5)^4+复合离子掺杂的(Bi0.5Na0.5)0.94Ba0.06Ti1-x(W0.5Mg0.5)xO3(BNBT-x WM)无铅陶瓷,研究了(W0.5Mg0.5)^4+复合离子掺杂量对BNBT陶瓷的表面形貌、微观结构,以及铁电、应变、压电、介电等电学性能的影响。结果表明:(W0.5Mg0.5)^4+复合离子进入了BNBT陶瓷的B位并形成了单一的钙钛矿结构,且陶瓷样品晶界清晰,结构致密。(W0.5Mg0.5)^4+掺杂增大了剩余极化强度和饱和极化强度。(W0.5Mg0.5)^4+复合离子的掺杂使电致应变曲线由蝴蝶形变为嫩芽形,在x=0.03时获得0.429%(质量分数)的高电致应变响应,d33*的最大值为833.1 pm/V,其外加高场仅有60 k V/cm。在x=0.02时其低场小信号的压电性能d33有235 p C/N。BNBT-x WM陶瓷的介电常数随着掺杂含量的增多逐渐降低且平坦化,同时向弛豫铁电体转变。
