The precursor prepared by coordinated co-precipitation was direct reduced by hydrogen to ultra-fine fibrous Fe-Ni alloy powder. The effects of concentrations of reactants, pH value, reaction temperature and additive o...The precursor prepared by coordinated co-precipitation was direct reduced by hydrogen to ultra-fine fibrous Fe-Ni alloy powder. The effects of concentrations of reactants, pH value, reaction temperature and additive on the preparation of precursor were systematically investigated. The structures, thermal decomposition processes and morphologies of the precursors were characterized by X-ray diffraction (XRD), thermal gravity-differential thermal analysis (TG-DTA) and scanning electron microscoy (SEM). The results show that using 2% polyvinylpyrrolidone (PVP) (in mass fraction) as additive, a well-dispersed precursor with a uniform morphology can be obtained in a solution with Fe2+ and Ni2+ total concentration (1:1) of 0.8 mol/L, pH value of 6.2 at 60 °C, and a pure and well dispersed fibrous iron-nickel powder can be prepared by direct reduction of this precursor in a mixed atmosphere of nitrogen and hydrogen at the temperature of 420 °C.展开更多
Al-4.9 Fe-4.9 Ni alloy powders have been synthesized by mechanical alloying. The rnechanically alloyed powders are consolidated by hot hydrostatic extrusion. The results show that extrusion tempereture. extrusion rati...Al-4.9 Fe-4.9 Ni alloy powders have been synthesized by mechanical alloying. The rnechanically alloyed powders are consolidated by hot hydrostatic extrusion. The results show that extrusion tempereture. extrusion ratio and lubricant have great effects on the quality of extruded rods and their mechanical properties, The mixture of graphite and glass powders as lubricant can prevent the oxidization of cold compacted billet by cladding the billet with this lubricant before heating. This technique greatly simplifies the conventional densification process of powders展开更多
Fine finishing of tungsten alloy is required to improve the surface quality of molds and precision instruments. Nevertheless, it is difficult to obtain high-quality surfaces as a result of grain boundary steps attribu...Fine finishing of tungsten alloy is required to improve the surface quality of molds and precision instruments. Nevertheless, it is difficult to obtain high-quality surfaces as a result of grain boundary steps attributed to differences in properties of two-phase microstructures. This paper presents a theoretical and experimental investigation on chemical mechanical polishing of W–Ni–Fe alloy. The mechanism of the boundary step generation is illustrated and a model of grain boundary step formation is proposed. The mechanism reveals the effects of mechanical and chemical actions in both surface roughness and material removal. The model was verified by the experiments and the results show that appropriately balancing the mechanical and chemical effects restrains the generation of boundary steps and leads to a fine surface quality with a high removal rate by citric acid-based slurry.展开更多
利用两阶段还原法对W Ni Fe复合氧化物粉末进行还原,控制还原工艺的参数制得纳米级W Ni Fe复合粉末。采用XRD对粉末进行物相分析,并计算晶粒尺寸;采用高倍SEM观察粉末形貌;对复合粉末的费氏粒度、比表面面积、氧含量等进行测定与分析,...利用两阶段还原法对W Ni Fe复合氧化物粉末进行还原,控制还原工艺的参数制得纳米级W Ni Fe复合粉末。采用XRD对粉末进行物相分析,并计算晶粒尺寸;采用高倍SEM观察粉末形貌;对复合粉末的费氏粒度、比表面面积、氧含量等进行测定与分析,研究还原温度和还原时间对粉末性能的影响。研究结果表明:当还原温度高于600℃时制得的复合粉末由W和(Ni,Fe)两相组成;粉末颗粒呈球形或近球形;还原温度和还原时间都对W Ni Fe复合粉末的性能有显著影响,当还原温度为700℃,还原时间为90min时,制备的颗粒为平均费氏粒度低于0.65μm,平均BET粒度小于100nm,晶粒粒径小于30nm,粉末氧含量小于0.23%的纳米级W Ni Fe复合粉末。展开更多
基金Project (20090162120080) supported by the Research Fund for Doctoral Program of Higher Education of ChinaProject (2010FJ3011)supported by the Program of Science and Technology of Hunan Province, ChinaProject supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University, China
文摘The precursor prepared by coordinated co-precipitation was direct reduced by hydrogen to ultra-fine fibrous Fe-Ni alloy powder. The effects of concentrations of reactants, pH value, reaction temperature and additive on the preparation of precursor were systematically investigated. The structures, thermal decomposition processes and morphologies of the precursors were characterized by X-ray diffraction (XRD), thermal gravity-differential thermal analysis (TG-DTA) and scanning electron microscoy (SEM). The results show that using 2% polyvinylpyrrolidone (PVP) (in mass fraction) as additive, a well-dispersed precursor with a uniform morphology can be obtained in a solution with Fe2+ and Ni2+ total concentration (1:1) of 0.8 mol/L, pH value of 6.2 at 60 °C, and a pure and well dispersed fibrous iron-nickel powder can be prepared by direct reduction of this precursor in a mixed atmosphere of nitrogen and hydrogen at the temperature of 420 °C.
文摘Al-4.9 Fe-4.9 Ni alloy powders have been synthesized by mechanical alloying. The rnechanically alloyed powders are consolidated by hot hydrostatic extrusion. The results show that extrusion tempereture. extrusion ratio and lubricant have great effects on the quality of extruded rods and their mechanical properties, The mixture of graphite and glass powders as lubricant can prevent the oxidization of cold compacted billet by cladding the billet with this lubricant before heating. This technique greatly simplifies the conventional densification process of powders
基金supported by National Key Research and Development Program (No. 2018YFA0702900)National Natural Science Foundation of China (No. 51975096)+1 种基金Science Challenge Project (No. TZ2018006-0101-01)Liao Ning Revitalization Talents Program (No. XLYC1807230)。
文摘Fine finishing of tungsten alloy is required to improve the surface quality of molds and precision instruments. Nevertheless, it is difficult to obtain high-quality surfaces as a result of grain boundary steps attributed to differences in properties of two-phase microstructures. This paper presents a theoretical and experimental investigation on chemical mechanical polishing of W–Ni–Fe alloy. The mechanism of the boundary step generation is illustrated and a model of grain boundary step formation is proposed. The mechanism reveals the effects of mechanical and chemical actions in both surface roughness and material removal. The model was verified by the experiments and the results show that appropriately balancing the mechanical and chemical effects restrains the generation of boundary steps and leads to a fine surface quality with a high removal rate by citric acid-based slurry.
文摘利用两阶段还原法对W Ni Fe复合氧化物粉末进行还原,控制还原工艺的参数制得纳米级W Ni Fe复合粉末。采用XRD对粉末进行物相分析,并计算晶粒尺寸;采用高倍SEM观察粉末形貌;对复合粉末的费氏粒度、比表面面积、氧含量等进行测定与分析,研究还原温度和还原时间对粉末性能的影响。研究结果表明:当还原温度高于600℃时制得的复合粉末由W和(Ni,Fe)两相组成;粉末颗粒呈球形或近球形;还原温度和还原时间都对W Ni Fe复合粉末的性能有显著影响,当还原温度为700℃,还原时间为90min时,制备的颗粒为平均费氏粒度低于0.65μm,平均BET粒度小于100nm,晶粒粒径小于30nm,粉末氧含量小于0.23%的纳米级W Ni Fe复合粉末。
