The high-temperature mechanical properties of 95W-3.5Ni-1.5Fe and 95W-4.5Ni-0.5Co alloys were investigated in the temperature range of room temperature to1100℃. The yield strength and tensile strengths declined gradu...The high-temperature mechanical properties of 95W-3.5Ni-1.5Fe and 95W-4.5Ni-0.5Co alloys were investigated in the temperature range of room temperature to1100℃. The yield strength and tensile strengths declined gradually, and the ductility of both alloys increased as the testing temperature was increased to 300℃. All the three properties reached a plateau at temperatures between 300 and 500℃ in the case of 95W-3.5Ni-l.5Fe and at temperatures between 350 and 700℃ in the case of 95W-4.5Ni-0.5Co. Thereafter, the ductility as well as yield and tensile strengths decreased considerably.展开更多
New TiAl alloys, containing 45 at.% A1, 7 at.% Nb, x at.% W, and 0.15 at.% B (x = 0, 0.2, 0.4, and 0.7) were prepared by arc melting and drop casting consequently. Using optical microscopy, scanning electron microsc...New TiAl alloys, containing 45 at.% A1, 7 at.% Nb, x at.% W, and 0.15 at.% B (x = 0, 0.2, 0.4, and 0.7) were prepared by arc melting and drop casting consequently. Using optical microscopy, scanning electron microscopy (SEM), and electron superprobe technologies, the effects of tungsten on the microstructural evolution of the TiA1 alloys, including the colony size and lamellar spacing, were analyzed. It was found that cellular structures and dendrites were formed in the as-cast TiA1 alloys, and heavy metals, such as niobium and tungsten, tend to segregate strongly at the interface of the cellular structures and dendrites. Trace tungsten can effectively impede the grain growth and narrow the interlamellar spacing. 0.4 at.% tungsten is more effective in refuting the microstructure of the TiAI alloys.展开更多
Ultrafine grain tungsten heavy alloys (WHAs) were successfully produced from the nano-crystalline powders using spark plasma sintering.The present study mainly discussed the effects of sintering temperature on the den...Ultrafine grain tungsten heavy alloys (WHAs) were successfully produced from the nano-crystalline powders using spark plasma sintering.The present study mainly discussed the effects of sintering temperature on the density,microstructure and mechanical properties of the alloys.The relative density of 98.12% was obtained at 1 050 ℃,and the tungsten grain size is about 871 nm.At 1 000 ℃-1 200 ℃,the mechanical properties of the alloys tend to first rise and then goes down.After SPS,the alloy exhibits improved hardness (84.3 HRA at 1 050 ℃) and bending strength (987.16 MPa at 1 100 ℃),due to the ultrafine-grained microstructure.The fracture mode after bending tests is mainly characterized as intergranular or intragranular fracture of W grains,interfacial debonding of W grains-binding phase and ductile tearing of binding phase.The EDS analysis reveals a certain proportion of solid solution between W and Ni-Fe binding phase.The good mechanical properties of the alloys can be attributed to grain refinement and solid solution strengthening.展开更多
A novel reduction technique has been developed to synthesize nano-sized tungsten heavy alloys powders and compared with the same powders processed by mechanical alloying technique. In the first method, nano-sized tung...A novel reduction technique has been developed to synthesize nano-sized tungsten heavy alloys powders and compared with the same powders processed by mechanical alloying technique. In the first method, nano-sized tungsten heavy alloys powders have been obtained by reduction of precursors obtained by spray drying of several appropriate aqueous solutions, which were made from salts containing tungsten, cobalt, and nickel. By adjusting the stoichiometry of the component of the solutions, it is possible to obtain the desired chemical composition of the tungsten heavy alloys powders. In the second method, highly pure elemental powders of tungsten heavy alloys have been mechanically alloyed in a tumbler ball mill for different milling time. The investigated tungsten heavy alloy powders with the composition (95%W-3.5%Ni-1.5%Fe), (93%W-4.5%Ni-1.0%Fe-1.5%Co), and (90%W-6%Ni-4%Cu) have been prepared using both methods. The prepared powders have been compacted at 70 bar (200 MPa) and sintered in vacuum furnace at 1400℃. Vacuum sintering was carried out to achieve full densification of the produced tungsten heavy alloys. The investigated materials were going to be evaluated the physical and mechanical properties of the sintered parts such as density;electrical conductivity, hardness, and transverse rupture strength. The results reveal that, the grain size of alloys fabricated by chemical reduction technique (53.1 - 63.8 nm) is smaller than that fabricated by mechanical alloying technique (56.4 - 71.4 nm).展开更多
The mechanical properties of regenerated W-alloys relating to the chemical purity and size of reclamation powders of 93W-Ni-Fe-Co(Mn)alloy chips,the structure of main constituents of the powders,as well as microstruet...The mechanical properties of regenerated W-alloys relating to the chemical purity and size of reclamation powders of 93W-Ni-Fe-Co(Mn)alloy chips,the structure of main constituents of the powders,as well as microstrueture and fractograph of regenerated W-alloys made by the reclamation powders,composition of W particle and binder phase,content,structure and distribution of main impurity elements have been studied by means of optical microscope, SEM,XRES.XRD,TEM,AES and chemical analysis.The feasibility of oxidation-reduc- tion process for reclamation and the possibility of praetical application of regenerated W-al- loys have been discussed.展开更多
The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size o...The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3 μm) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1 465 ℃ for 30 min in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquid-phase sintered alloys using original tungsten powders due to lower sintering temperature at 1 465 ℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.展开更多
Tungsten heavy alloys are aggregates of particles of tungsten bonded with Ni/Fe or Ni/Cu via liquid-phase sintering. The sub-micrometer Ta Co powder was added to this aggregate to strengthen the bonding phase. It is f...Tungsten heavy alloys are aggregates of particles of tungsten bonded with Ni/Fe or Ni/Cu via liquid-phase sintering. The sub-micrometer Ta Co powder was added to this aggregate to strengthen the bonding phase. It is found that the main fr acture pattern of the alloys is cleavage of tungsten grains and ductile rupture of bond phase,leading to improved tensile strength and elongation. Dopant Ta ca n act as grain size inhibitor in tungsten heavy alloys.展开更多
Against protection requirements for high-speed fragments on the ground weapons,we carried out the research work of crushing mechanism at different impact speeds ofφ8.7 mm spherical tungsten alloy,the penetration to 6...Against protection requirements for high-speed fragments on the ground weapons,we carried out the research work of crushing mechanism at different impact speeds ofφ8.7 mm spherical tungsten alloy,the penetration to 603 armor steel was completed by 20 mm ballistic gun,and the ANSYS/LS-DYNA software was used to complete the numerical calculation of the penetration.We find that there are different crushing mechanisms of spherical tungsten alloy with different speeds and low speed,the crushing mechanism of fragment is mainly controlled by overall plastic deformation,shearing stripping,and squeezing at a high pressure and a high speed.The crushing mechanism will have a spallation phenomenon in addition to the crushing mechanism under high pressure.展开更多
锆合金因其优良的耐腐蚀性能,常用于制造核工业器件,受到研究者广泛关注。采用钨极氩弧焊作为焊接方法,使用ZrTiNb合金作为焊接材料,分别焊接了5、10、20 mm 3种尺寸的焊样。所得焊接接头焊缝区微观组织为粗大的片层集束和少量的篮网状...锆合金因其优良的耐腐蚀性能,常用于制造核工业器件,受到研究者广泛关注。采用钨极氩弧焊作为焊接方法,使用ZrTiNb合金作为焊接材料,分别焊接了5、10、20 mm 3种尺寸的焊样。所得焊接接头焊缝区微观组织为粗大的片层集束和少量的篮网状魏氏组织,组织形态与冷却速率相关;熔合区微观组织为较小的魏氏体晶粒,其与热影响区存在明显的分界线;热影响区微观组织为不规则锯齿状等轴α相晶粒;母材区微观组织为铸态α等轴晶粒。随着焊缝距离增加,晶粒尺寸呈现递减趋势。对焊缝进行了力学性能测试,结果表明,随着试样厚度增加,其塑性延伸强度、抗拉强度呈现先增加后下降的趋势,并在20 mm的厚度下出现明显下降。10、20 mm样品断后伸长率与断面收缩率相对于5 mm试样呈现增加的趋势,但10 mm和20 mm样品性能相近。展开更多
文摘The high-temperature mechanical properties of 95W-3.5Ni-1.5Fe and 95W-4.5Ni-0.5Co alloys were investigated in the temperature range of room temperature to1100℃. The yield strength and tensile strengths declined gradually, and the ductility of both alloys increased as the testing temperature was increased to 300℃. All the three properties reached a plateau at temperatures between 300 and 500℃ in the case of 95W-3.5Ni-l.5Fe and at temperatures between 350 and 700℃ in the case of 95W-4.5Ni-0.5Co. Thereafter, the ductility as well as yield and tensile strengths decreased considerably.
文摘New TiAl alloys, containing 45 at.% A1, 7 at.% Nb, x at.% W, and 0.15 at.% B (x = 0, 0.2, 0.4, and 0.7) were prepared by arc melting and drop casting consequently. Using optical microscopy, scanning electron microscopy (SEM), and electron superprobe technologies, the effects of tungsten on the microstructural evolution of the TiA1 alloys, including the colony size and lamellar spacing, were analyzed. It was found that cellular structures and dendrites were formed in the as-cast TiA1 alloys, and heavy metals, such as niobium and tungsten, tend to segregate strongly at the interface of the cellular structures and dendrites. Trace tungsten can effectively impede the grain growth and narrow the interlamellar spacing. 0.4 at.% tungsten is more effective in refuting the microstructure of the TiAI alloys.
基金the National Key Research and Development Plan of China(2017YFB0310400)the National Natural Science Foundation of China(Nos.5167020705 and 51902233)the Self-determined and Innovative Research Funds of WHUT(2019III059XZ)。
文摘Ultrafine grain tungsten heavy alloys (WHAs) were successfully produced from the nano-crystalline powders using spark plasma sintering.The present study mainly discussed the effects of sintering temperature on the density,microstructure and mechanical properties of the alloys.The relative density of 98.12% was obtained at 1 050 ℃,and the tungsten grain size is about 871 nm.At 1 000 ℃-1 200 ℃,the mechanical properties of the alloys tend to first rise and then goes down.After SPS,the alloy exhibits improved hardness (84.3 HRA at 1 050 ℃) and bending strength (987.16 MPa at 1 100 ℃),due to the ultrafine-grained microstructure.The fracture mode after bending tests is mainly characterized as intergranular or intragranular fracture of W grains,interfacial debonding of W grains-binding phase and ductile tearing of binding phase.The EDS analysis reveals a certain proportion of solid solution between W and Ni-Fe binding phase.The good mechanical properties of the alloys can be attributed to grain refinement and solid solution strengthening.
文摘A novel reduction technique has been developed to synthesize nano-sized tungsten heavy alloys powders and compared with the same powders processed by mechanical alloying technique. In the first method, nano-sized tungsten heavy alloys powders have been obtained by reduction of precursors obtained by spray drying of several appropriate aqueous solutions, which were made from salts containing tungsten, cobalt, and nickel. By adjusting the stoichiometry of the component of the solutions, it is possible to obtain the desired chemical composition of the tungsten heavy alloys powders. In the second method, highly pure elemental powders of tungsten heavy alloys have been mechanically alloyed in a tumbler ball mill for different milling time. The investigated tungsten heavy alloy powders with the composition (95%W-3.5%Ni-1.5%Fe), (93%W-4.5%Ni-1.0%Fe-1.5%Co), and (90%W-6%Ni-4%Cu) have been prepared using both methods. The prepared powders have been compacted at 70 bar (200 MPa) and sintered in vacuum furnace at 1400℃. Vacuum sintering was carried out to achieve full densification of the produced tungsten heavy alloys. The investigated materials were going to be evaluated the physical and mechanical properties of the sintered parts such as density;electrical conductivity, hardness, and transverse rupture strength. The results reveal that, the grain size of alloys fabricated by chemical reduction technique (53.1 - 63.8 nm) is smaller than that fabricated by mechanical alloying technique (56.4 - 71.4 nm).
文摘The mechanical properties of regenerated W-alloys relating to the chemical purity and size of reclamation powders of 93W-Ni-Fe-Co(Mn)alloy chips,the structure of main constituents of the powders,as well as microstrueture and fractograph of regenerated W-alloys made by the reclamation powders,composition of W particle and binder phase,content,structure and distribution of main impurity elements have been studied by means of optical microscope, SEM,XRES.XRD,TEM,AES and chemical analysis.The feasibility of oxidation-reduc- tion process for reclamation and the possibility of praetical application of regenerated W-al- loys have been discussed.
文摘The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3 μm) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1 465 ℃ for 30 min in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquid-phase sintered alloys using original tungsten powders due to lower sintering temperature at 1 465 ℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.
文摘Tungsten heavy alloys are aggregates of particles of tungsten bonded with Ni/Fe or Ni/Cu via liquid-phase sintering. The sub-micrometer Ta Co powder was added to this aggregate to strengthen the bonding phase. It is found that the main fr acture pattern of the alloys is cleavage of tungsten grains and ductile rupture of bond phase,leading to improved tensile strength and elongation. Dopant Ta ca n act as grain size inhibitor in tungsten heavy alloys.
基金Funded by the National Defense Technology Key Laboratory of Impact Environmental Materials。
文摘Against protection requirements for high-speed fragments on the ground weapons,we carried out the research work of crushing mechanism at different impact speeds ofφ8.7 mm spherical tungsten alloy,the penetration to 603 armor steel was completed by 20 mm ballistic gun,and the ANSYS/LS-DYNA software was used to complete the numerical calculation of the penetration.We find that there are different crushing mechanisms of spherical tungsten alloy with different speeds and low speed,the crushing mechanism of fragment is mainly controlled by overall plastic deformation,shearing stripping,and squeezing at a high pressure and a high speed.The crushing mechanism will have a spallation phenomenon in addition to the crushing mechanism under high pressure.