Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts wer...Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts were also characterized.Experimental results showed that welding at a speed of 8 mm/s and a wire feeding speed of 4.0 m/min was suitable to manufacture thin-walled parts,and the reciprocating scanning method could be adopted to manufacture thick-walled parts.The thin-walled parts of the C+P mode had fewer pores than those of the cold metal transfer(CMT)mode.The thin-and thick-walled parts of the C+P mode showed maximum tensile strengths of 172 and 178 MPa,respectively.Hardness decreased at the interface and in the coarse dendrite and increased in the refined grain area.展开更多
Cold Metal Transfer technology has revolutionized the welding of dissimilar metals and thicker materials by producing improved weld bead aesthetics with controlled metal deposition and low heat-input. In this study, t...Cold Metal Transfer technology has revolutionized the welding of dissimilar metals and thicker materials by producing improved weld bead aesthetics with controlled metal deposition and low heat-input. In this study, the process, weld combinations, laser-CMT hybrid welding and applications of CMT welding are critically reviewed. Microstructure and other weld characteristics have been discussed at length for various base metal combinations. Particularly, the welding of aluminium and steel with better results has been possible with CMT Welding. The results reviewed in this article indicate that the CMT-Laser hybrid welding is more preferable to Laser or Laser hybrid welding. CMT welding has found applications in automobile industries, defence sectors and power plants as a method of additive manufacturing.展开更多
Two dissimilar materials, aluminum alloy and aluminum-coated steel, were joined by cold metal transfer process using AlSi5 filler wire. To this end, the steel was coated with Al-Si. The steel did not melt and aluminum...Two dissimilar materials, aluminum alloy and aluminum-coated steel, were joined by cold metal transfer process using AlSi5 filler wire. To this end, the steel was coated with Al-Si. The steel did not melt and aluminum was melt to form the joint during the process, it was actually cold metal transfer welding-brazing. The macrostructure, microstructure, alloy element distribution, and inter-metallic compounds were analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. It was found that the Al-Si coating dissolved into the weld metal. The pre-existing thin Fe-Al- Si ternary inter-metallic compounds in the interface between the Ak-Si coating layer and base metal steel also partially dissolved into the weld zone, tending to reduce the thickness of inter-metallic compounds. Approximate 3 μm thick undissolved intermetallic compound was found at the interface after welding which could guarantee sound bonding strength in dissimilar materials joining. The sample was fractured at the fusion zone near the aluminum side in the tensile test. The ultimate tensile strength was about 156 MPa, and the fracture mode is ductile failure in nature according to its morphology.展开更多
Cold metal transfer with polarity⁃exchanging is a new integrated welding technology based on MIG.Due to the alternation of the positive and negative polarities of the wire,favorable control upon the deposition rate an...Cold metal transfer with polarity⁃exchanging is a new integrated welding technology based on MIG.Due to the alternation of the positive and negative polarities of the wire,favorable control upon the deposition rate and the welding shape coefficient was obtained in order to meet the desired joint design,and the related controlling principles and joint characteristics were reported.Droplet transfer physical behavior exhibited strong dependability on the studied welding parameters,such as welding voltage,welding current,wire feeding speed,and polarity⁃exchanging.This welding technology provides a new way for the welding of body⁃in⁃white(BIW)thin sheet with special demands.Moreover,the typical quality defects of MIG were greatly improved.Our study provides important technical information from the perspective of industrial application of MIG and sheds light on the higher application level of MIG in BIW welding.展开更多
We have established a caesium double magneto-optical trap (MOT) system for cavity-QED experiment, and demonstrated the continuous transfer of cold caesium atoms from the vapour-cell MOT with a pressure of - 1 ×...We have established a caesium double magneto-optical trap (MOT) system for cavity-QED experiment, and demonstrated the continuous transfer of cold caesium atoms from the vapour-cell MOT with a pressure of - 1 × 10^-6 Pa to the ultra-high-vacuum (UHV) MOT with a pressure of - 8 × 10^-8 Pa via a focused continuous-wave transfer laser beam. The effect of frequency detuning as well as the intensity of the transfer beam is systematically investigated, which makes the transverse cooling adequate before the atoms leak out of the vapour-cell MOT to reduce divergence of the cold atomic beam. The typical cold atomic flux got from vapour-cell MOT is - 2 × 10^7 atoms/s. About 5 × 10^6 caesium atoms are recaptured in the UHV MOT.展开更多
A cold Rydberg gas, with its atoms prepared initially all in the excited state <span style="white-space:nowrap;">|<em>n</em><sub>0</sub>></span> , with <em>n</...A cold Rydberg gas, with its atoms prepared initially all in the excited state <span style="white-space:nowrap;">|<em>n</em><sub>0</sub>></span> , with <em>n</em><sub>0 </sub><span style="white-space:nowrap;">»</span>1, contains an excessive amount of energy, and presumably is to relax by the Penning-type <em>molecular auto-ionization</em> (<em>MAI</em>), in which a portion of excess energy of one atom is given to another near-by atom and ionizing it. Its complementary process, the <em>resonant energy transfer</em> (<em>RET</em>), is discussed, in which the excess energy of one atom is used on another to form a hyper-excited atomic state <span style="white-space:normal;">|</span><em style="white-space:normal;">n</em><sub style="white-space:normal;"><em>a</em></sub><span style="white-space:normal;">></span> with <em>n</em><sub><em>a</em></sub><span style="white-space:nowrap;">»</span><em style="white-space:normal;">n</em><sub style="white-space:normal;">0</sub>. This process is always present, provided certain resonance energy conditions are satisfied. In this report, the <em>n</em><sub>0</sub> and density dependences of the RET rates are studied in detail, employing a simple model: 1) at low densities, the RET is mediated by the dipole-dipole coupling <em>V</em><sub><em>dd</em></sub> and its rates are generally much smaller than that of MAI, especially for small <em>n</em><sub>0</sub>. But 2) as the density increases, our model shows that the rates become of comparable magnitude or even larger than the MAI rates. The<em> V</em><sub><em>dd</em></sub> is no longer adequate. We, then construct a semi-empirical potential to describe the RET process. 3) At high densities, we show that the atomic orbital of <span style="white-space:normal;">|</span><em style="white-space:normal;">n</em><sub style="white-space:normal;"><em>a</em></sub><span style="white-space:normal;">></span> overlaps with that of neighboring atoms, and the electron-electron potential becomes prominent, resulting in much higher rates.展开更多
综述了涉及工程应用的冷丝熔化极气体保护焊(Cold wire gas metal arc welding,CW-GMAW)熔滴过渡形态特征。结果表明,在大电流、强规范、富氩混合气体保护下,CW-GMAW工艺的熔滴过渡形态呈喷射过渡;当电流较小、电弧电压较低时,可能为滴...综述了涉及工程应用的冷丝熔化极气体保护焊(Cold wire gas metal arc welding,CW-GMAW)熔滴过渡形态特征。结果表明,在大电流、强规范、富氩混合气体保护下,CW-GMAW工艺的熔滴过渡形态呈喷射过渡;当电流较小、电弧电压较低时,可能为滴状过渡,甚至在弧压很低时,呈现短路过渡形态。该工艺电弧发生偏向冷丝的位移,弧长变短甚至发生短路,与冷丝送进速率比增高及冷丝在电弧中产生大量金属蒸气时弧柱电阻下降有关。在具有富氩混合保护气体的相同工艺参数下,CWGMAW转变电流比GMAW降低了4%~7%。焊接工艺参数对CW-GMAW和GMAW工艺熔滴过渡形态的影响规律大致相近,但前者因涉及冷丝送进速率比和电极焊丝送进速度,以及它们的匹配等,使焊接电流的影响更为复杂。展开更多
基金the National Natural Science Foundation of China(Nos.51605276 and51905333)Shanghai Sailing Program(No.19YF1418100)+2 种基金Shanghai Science and Technology Committee Innovation Grant(Nos.17JC1400600 and 17JC1400601)Karamay Science and Technology Major Project(No.2018ZD002B)Aid for Xinjiang Science and Technology Project(No2019E0235)。
文摘Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts were also characterized.Experimental results showed that welding at a speed of 8 mm/s and a wire feeding speed of 4.0 m/min was suitable to manufacture thin-walled parts,and the reciprocating scanning method could be adopted to manufacture thick-walled parts.The thin-walled parts of the C+P mode had fewer pores than those of the cold metal transfer(CMT)mode.The thin-and thick-walled parts of the C+P mode showed maximum tensile strengths of 172 and 178 MPa,respectively.Hardness decreased at the interface and in the coarse dendrite and increased in the refined grain area.
文摘Cold Metal Transfer technology has revolutionized the welding of dissimilar metals and thicker materials by producing improved weld bead aesthetics with controlled metal deposition and low heat-input. In this study, the process, weld combinations, laser-CMT hybrid welding and applications of CMT welding are critically reviewed. Microstructure and other weld characteristics have been discussed at length for various base metal combinations. Particularly, the welding of aluminium and steel with better results has been possible with CMT Welding. The results reviewed in this article indicate that the CMT-Laser hybrid welding is more preferable to Laser or Laser hybrid welding. CMT welding has found applications in automobile industries, defence sectors and power plants as a method of additive manufacturing.
基金This research is supported by the National Natural Science Foundation of China ( No. 51005101 ), Jiamusi University Scientific Research Project (12010 -118) and State Key Laboratory of Advanced Welding Production Technology Project (AWJ-M13 -04).
文摘Two dissimilar materials, aluminum alloy and aluminum-coated steel, were joined by cold metal transfer process using AlSi5 filler wire. To this end, the steel was coated with Al-Si. The steel did not melt and aluminum was melt to form the joint during the process, it was actually cold metal transfer welding-brazing. The macrostructure, microstructure, alloy element distribution, and inter-metallic compounds were analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. It was found that the Al-Si coating dissolved into the weld metal. The pre-existing thin Fe-Al- Si ternary inter-metallic compounds in the interface between the Ak-Si coating layer and base metal steel also partially dissolved into the weld zone, tending to reduce the thickness of inter-metallic compounds. Approximate 3 μm thick undissolved intermetallic compound was found at the interface after welding which could guarantee sound bonding strength in dissimilar materials joining. The sample was fractured at the fusion zone near the aluminum side in the tensile test. The ultimate tensile strength was about 156 MPa, and the fracture mode is ductile failure in nature according to its morphology.
文摘Cold metal transfer with polarity⁃exchanging is a new integrated welding technology based on MIG.Due to the alternation of the positive and negative polarities of the wire,favorable control upon the deposition rate and the welding shape coefficient was obtained in order to meet the desired joint design,and the related controlling principles and joint characteristics were reported.Droplet transfer physical behavior exhibited strong dependability on the studied welding parameters,such as welding voltage,welding current,wire feeding speed,and polarity⁃exchanging.This welding technology provides a new way for the welding of body⁃in⁃white(BIW)thin sheet with special demands.Moreover,the typical quality defects of MIG were greatly improved.Our study provides important technical information from the perspective of industrial application of MIG and sheds light on the higher application level of MIG in BIW welding.
基金Project supported by the Natural Science Foundation of China (Grant Nos 60578018 10434080, and 10374062), the Sino-Russia Joint Project (NSFC-RFBR), by the Key Scientific Project of the Education Ministry of China (Grant No 204019), the Cultivation Fund of the Key Scientific and Technical Innovation Project (Grant No 705010) and the Program for Innovative Research Team in University (IRT0516) from the Education Ministry of China, and also by the Research Funds for Youth Academic Leaders of Shanxi Province.
文摘We have established a caesium double magneto-optical trap (MOT) system for cavity-QED experiment, and demonstrated the continuous transfer of cold caesium atoms from the vapour-cell MOT with a pressure of - 1 × 10^-6 Pa to the ultra-high-vacuum (UHV) MOT with a pressure of - 8 × 10^-8 Pa via a focused continuous-wave transfer laser beam. The effect of frequency detuning as well as the intensity of the transfer beam is systematically investigated, which makes the transverse cooling adequate before the atoms leak out of the vapour-cell MOT to reduce divergence of the cold atomic beam. The typical cold atomic flux got from vapour-cell MOT is - 2 × 10^7 atoms/s. About 5 × 10^6 caesium atoms are recaptured in the UHV MOT.
文摘A cold Rydberg gas, with its atoms prepared initially all in the excited state <span style="white-space:nowrap;">|<em>n</em><sub>0</sub>></span> , with <em>n</em><sub>0 </sub><span style="white-space:nowrap;">»</span>1, contains an excessive amount of energy, and presumably is to relax by the Penning-type <em>molecular auto-ionization</em> (<em>MAI</em>), in which a portion of excess energy of one atom is given to another near-by atom and ionizing it. Its complementary process, the <em>resonant energy transfer</em> (<em>RET</em>), is discussed, in which the excess energy of one atom is used on another to form a hyper-excited atomic state <span style="white-space:normal;">|</span><em style="white-space:normal;">n</em><sub style="white-space:normal;"><em>a</em></sub><span style="white-space:normal;">></span> with <em>n</em><sub><em>a</em></sub><span style="white-space:nowrap;">»</span><em style="white-space:normal;">n</em><sub style="white-space:normal;">0</sub>. This process is always present, provided certain resonance energy conditions are satisfied. In this report, the <em>n</em><sub>0</sub> and density dependences of the RET rates are studied in detail, employing a simple model: 1) at low densities, the RET is mediated by the dipole-dipole coupling <em>V</em><sub><em>dd</em></sub> and its rates are generally much smaller than that of MAI, especially for small <em>n</em><sub>0</sub>. But 2) as the density increases, our model shows that the rates become of comparable magnitude or even larger than the MAI rates. The<em> V</em><sub><em>dd</em></sub> is no longer adequate. We, then construct a semi-empirical potential to describe the RET process. 3) At high densities, we show that the atomic orbital of <span style="white-space:normal;">|</span><em style="white-space:normal;">n</em><sub style="white-space:normal;"><em>a</em></sub><span style="white-space:normal;">></span> overlaps with that of neighboring atoms, and the electron-electron potential becomes prominent, resulting in much higher rates.
文摘综述了涉及工程应用的冷丝熔化极气体保护焊(Cold wire gas metal arc welding,CW-GMAW)熔滴过渡形态特征。结果表明,在大电流、强规范、富氩混合气体保护下,CW-GMAW工艺的熔滴过渡形态呈喷射过渡;当电流较小、电弧电压较低时,可能为滴状过渡,甚至在弧压很低时,呈现短路过渡形态。该工艺电弧发生偏向冷丝的位移,弧长变短甚至发生短路,与冷丝送进速率比增高及冷丝在电弧中产生大量金属蒸气时弧柱电阻下降有关。在具有富氩混合保护气体的相同工艺参数下,CWGMAW转变电流比GMAW降低了4%~7%。焊接工艺参数对CW-GMAW和GMAW工艺熔滴过渡形态的影响规律大致相近,但前者因涉及冷丝送进速率比和电极焊丝送进速度,以及它们的匹配等,使焊接电流的影响更为复杂。