Press hardened steel(PHS)plays a key role in the manufacture of anti-collision structural components.The formation of δ-ferrite is a suffering issue for the laser welding of Al-Si coated PHS.Oscillating laser was use...Press hardened steel(PHS)plays a key role in the manufacture of anti-collision structural components.The formation of δ-ferrite is a suffering issue for the laser welding of Al-Si coated PHS.Oscillating laser was used to weld Al-Si coated 1.5 GPa PHS and novel 2 GPa PHS,and the effect of laser offset on the microstructure and properties of the dissimilar welded joints was studied.The results showed that a perfect weld profile was achieved by laser offset welding(LOW),without any welding defects.The δ-ferrite formed in as-received welds of laser alignment welding(LAW)with high Al content(up to 2.9 wt.%),but it disappeared with the laser offset to 2 GPa PHS,and the maximum Al content in the segregation zone reduced to 1.2 wt.%.After post-welding heat treatment,the δ-ferrite was coarsened and theα-ferrite formed in the secondary Al-rich area for the high Ac3 temperature,but the α-ferrite was few and fine in LOW welds.The hardness in the LAW welds was lower than that in the LOW welds,due to the presence of δ-ferrite,as well as less carbon content and Ti and V alloying elements.The tensile strength(1561 MPa)and elongation(5.4%)with LOW were higher than those with LAW(1490 MPa,3.1%),and the fracture occurred in the Al-Si coated PHS.It is indicated that adjusting the laser offset is effective to prevent the formation of δ-ferrite and is potential to avoid the formation of α-ferrite.It also provides a wide heat treatment temperature window for the dissimilar welds of 1.5 GPa PHS and novel 2 GPa PHS.展开更多
A series of photochromic diarylethene derivatives containing different fluorophores was synthesized by the Sonogashira coupling reaction and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR and mass spect...A series of photochromic diarylethene derivatives containing different fluorophores was synthesized by the Sonogashira coupling reaction and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR and mass spectroscopy. Photochromic conversion of Cz-MS was observed and its structural change was confirmed by proton NMR. Switchable absorption and emission phenomena were observed for these molecules. These phenomena were attributed to the reversible photochromic fluorescence resonance energy transfer (pcFRET) process. The design of this novel photochromic system of Py-4MS enables information to be processed in a non-destructive manner. This overcomes the problem of the destructive nature of tracking photochromism using ultraviolet (UV)-vis spectroscopy.展开更多
基金financially supported by the funds of the National Natural Science Foundation of China(Nos.52005357 and U1908224)the support of Postdoctoral Research Foundation of China(2022M712308)Liaoning Revitalization Talents Program(No.XLYC2007066).
文摘Press hardened steel(PHS)plays a key role in the manufacture of anti-collision structural components.The formation of δ-ferrite is a suffering issue for the laser welding of Al-Si coated PHS.Oscillating laser was used to weld Al-Si coated 1.5 GPa PHS and novel 2 GPa PHS,and the effect of laser offset on the microstructure and properties of the dissimilar welded joints was studied.The results showed that a perfect weld profile was achieved by laser offset welding(LOW),without any welding defects.The δ-ferrite formed in as-received welds of laser alignment welding(LAW)with high Al content(up to 2.9 wt.%),but it disappeared with the laser offset to 2 GPa PHS,and the maximum Al content in the segregation zone reduced to 1.2 wt.%.After post-welding heat treatment,the δ-ferrite was coarsened and theα-ferrite formed in the secondary Al-rich area for the high Ac3 temperature,but the α-ferrite was few and fine in LOW welds.The hardness in the LAW welds was lower than that in the LOW welds,due to the presence of δ-ferrite,as well as less carbon content and Ti and V alloying elements.The tensile strength(1561 MPa)and elongation(5.4%)with LOW were higher than those with LAW(1490 MPa,3.1%),and the fracture occurred in the Al-Si coated PHS.It is indicated that adjusting the laser offset is effective to prevent the formation of δ-ferrite and is potential to avoid the formation of α-ferrite.It also provides a wide heat treatment temperature window for the dissimilar welds of 1.5 GPa PHS and novel 2 GPa PHS.
基金Project supported by the National Natural Science Foundation of China (No. 20674070)the Natural Science Foundation of Zhejiang Province (No. R404109), China
文摘A series of photochromic diarylethene derivatives containing different fluorophores was synthesized by the Sonogashira coupling reaction and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR and mass spectroscopy. Photochromic conversion of Cz-MS was observed and its structural change was confirmed by proton NMR. Switchable absorption and emission phenomena were observed for these molecules. These phenomena were attributed to the reversible photochromic fluorescence resonance energy transfer (pcFRET) process. The design of this novel photochromic system of Py-4MS enables information to be processed in a non-destructive manner. This overcomes the problem of the destructive nature of tracking photochromism using ultraviolet (UV)-vis spectroscopy.
