Electron beam welding of Ti-15-3 alloy to 304 stainless steel （STS） using a copper filler metal was carried out. The temperature fields and stress distributions in the Ti/Fe and Ti/Cu/Fe joint during the welding pro...Electron beam welding of Ti-15-3 alloy to 304 stainless steel （STS） using a copper filler metal was carried out. The temperature fields and stress distributions in the Ti/Fe and Ti/Cu/Fe joint during the welding process were numerically simulated and experimentally measured. The results show that the rotated parabola body heat source is fit for the simulation of the electron beam welding. The temperature distribution is asymmetric along the weld center and the temperature in the titanium alloy plate is higher than that in the 304 STS plate. The thermal stress also appears to be in asymmetric distribution. The residual tensile stress mainly exists in the weld at the 304 STS side. The copper filler metal decreases the peak temperature and temperature grade in the joint as well as the residual stress. The longitudinal and lateral residual tensile strengths reduce by 66 MPa and 31 MPa, respectively. From the temperature and residual stress, it is concluded that copper is a good filler metal candidate for the electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel.展开更多
Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with a copper sheet as interlayer was carried out.Microstructures of the joint were studied by optical microscopy(OM),scanning electron microscopy...Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with a copper sheet as interlayer was carried out.Microstructures of the joint were studied by optical microscopy(OM),scanning electron microscopy(SEM) and X-ray diffractometry(XRD).In addition,the mechanical properties of the joint were evaluated by tensile test and the microhardness was measured.These two alloys were successfully welded by adding copper transition layer into the weld.Solid solution with a certain thickness was located at the interfaces between weld and base metal in both sides.Regions inside the weld and near the stainless steel were characterized by solid solution of copper with TiFe2 intermetallics dispersedly distributed in it.While weld near titanium alloy contained Ti-Cu and Ti-Fe-Cu intermetallics layer,in which the hardness of weld came to the highest value.Brittle fracture occurred in the intermetallics layer when the joint was stretched.展开更多
A series of metamorphic high electron mobility transistors （MMHEMTs） with different Ⅴ/Ⅲ flux ratios are grown on CaAs （001） substrates by molecular beam epitaxy （MBE）. The samples are analysed by using atomic ...A series of metamorphic high electron mobility transistors （MMHEMTs） with different Ⅴ/Ⅲ flux ratios are grown on CaAs （001） substrates by molecular beam epitaxy （MBE）. The samples are analysed by using atomic force microscopy （AFM）, Hall measurement, and low temperature photoluminescence （PL）. The optimum Ⅴ/Ⅲ ratio in a range from 15 to 60 for the growth of MMHEMTs is found to be around 40. At this ratio, the root mean square （RMS） roughness of the material is only 2.02 nm; a room-temperature mobility and a sheet electron density are obtained to be 10610.0cm^2/（V.s） and 3.26×10^12cm^-2 respectively. These results are equivalent to those obtained for the same structure grown on InP substrate. There are two peaks in the PL spectrum of the structure, corresponding to two sub-energy levels of the In0.53Ga0.47As quantum well. It is found that the photoluminescence intensities of the two peaks vary with the Ⅴ/Ⅲ ratio, for which the reasons are discussed.展开更多
The interaction of a relativistic electron beam (REB) with inhomogeneous, magneto-active, relativistic warm plasma is theoretically investigated. The nonlinear formation of waves at second and triple frequency at the ...The interaction of a relativistic electron beam (REB) with inhomogeneous, magneto-active, relativistic warm plasma is theoretically investigated. The nonlinear formation of waves at second and triple frequency at the inlet of the beam into the plasma is investigated. Effects of external static or oscillating magnetic field are considered. Nonlinear effects associated with the generation of second and triple harmonics, play an important role in the process of energy transfer from the beam to the plasma as compared with linear stage.展开更多
基金Foundation item:Project (2010CB731704) supported by the National Basic Research Program of ChinaProject (51075189) supported by the National Natural Science Foundation of China
文摘Electron beam welding of Ti-15-3 alloy to 304 stainless steel （STS） using a copper filler metal was carried out. The temperature fields and stress distributions in the Ti/Fe and Ti/Cu/Fe joint during the welding process were numerically simulated and experimentally measured. The results show that the rotated parabola body heat source is fit for the simulation of the electron beam welding. The temperature distribution is asymmetric along the weld center and the temperature in the titanium alloy plate is higher than that in the 304 STS plate. The thermal stress also appears to be in asymmetric distribution. The residual tensile stress mainly exists in the weld at the 304 STS side. The copper filler metal decreases the peak temperature and temperature grade in the joint as well as the residual stress. The longitudinal and lateral residual tensile strengths reduce by 66 MPa and 31 MPa, respectively. From the temperature and residual stress, it is concluded that copper is a good filler metal candidate for the electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel.
文摘Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with a copper sheet as interlayer was carried out.Microstructures of the joint were studied by optical microscopy(OM),scanning electron microscopy(SEM) and X-ray diffractometry(XRD).In addition,the mechanical properties of the joint were evaluated by tensile test and the microhardness was measured.These two alloys were successfully welded by adding copper transition layer into the weld.Solid solution with a certain thickness was located at the interfaces between weld and base metal in both sides.Regions inside the weld and near the stainless steel were characterized by solid solution of copper with TiFe2 intermetallics dispersedly distributed in it.While weld near titanium alloy contained Ti-Cu and Ti-Fe-Cu intermetallics layer,in which the hardness of weld came to the highest value.Brittle fracture occurred in the intermetallics layer when the joint was stretched.
文摘A series of metamorphic high electron mobility transistors （MMHEMTs） with different Ⅴ/Ⅲ flux ratios are grown on CaAs （001） substrates by molecular beam epitaxy （MBE）. The samples are analysed by using atomic force microscopy （AFM）, Hall measurement, and low temperature photoluminescence （PL）. The optimum Ⅴ/Ⅲ ratio in a range from 15 to 60 for the growth of MMHEMTs is found to be around 40. At this ratio, the root mean square （RMS） roughness of the material is only 2.02 nm; a room-temperature mobility and a sheet electron density are obtained to be 10610.0cm^2/（V.s） and 3.26×10^12cm^-2 respectively. These results are equivalent to those obtained for the same structure grown on InP substrate. There are two peaks in the PL spectrum of the structure, corresponding to two sub-energy levels of the In0.53Ga0.47As quantum well. It is found that the photoluminescence intensities of the two peaks vary with the Ⅴ/Ⅲ ratio, for which the reasons are discussed.
文摘The interaction of a relativistic electron beam (REB) with inhomogeneous, magneto-active, relativistic warm plasma is theoretically investigated. The nonlinear formation of waves at second and triple frequency at the inlet of the beam into the plasma is investigated. Effects of external static or oscillating magnetic field are considered. Nonlinear effects associated with the generation of second and triple harmonics, play an important role in the process of energy transfer from the beam to the plasma as compared with linear stage.
