Electron beam welding of 304 stainless steel to QCr0.8 copper alloy with copper filler wire

Electron beam welding （EBW） of 304 stainless steel to QCr0.8 copper alloy with copper filler wire was carried out. Orthogonal experiment was performed to investigate the effects of process parameters on the tensile strength of the joints, and the process parameters were optimized. The optimum process parameters are as follows：beam current of 30 mA, welding speed of 100 mm/min, wire feed rate of 1 m/min and beam offset of-0.3 mm. The microstructures of the optimum joint were studied. The results indicate that the weld is mainly composed of dendriticαphase with little globularεphase, and copper inhomogeneity only occurs at the top of the fusion zone. In addition, a melted region without mixing exists near the weld junction of copper side. This region with a coarser grain size is the weakest section of the joints. It is found that the microhardness of the weld decreases with the increase of the copper content in solid solution. The highest tensile strength of the joint is 276 MPa.

Influences of different filler metals on electron beam welding of titanium alloy to stainless steel

Electron beam welding experiments of titanium alloy to stainless steel were carried out with different filler metals, such as Ni, V, and Cu. Microstructures of the joints were examined by optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Mechanical properties of the joints were evaluated according to tensile strength and microhardness. As a result, influences of filler metals on microstructures and mechanical properties of electron beam welded titanium-stainless steel joints were discussed. The results showed that all the filler metals were helpful to restrain the Ti-Fe intermetallics. The welds with different filler metals were all characterized by solid solution and interfacial intermetallics. For each type of the filler metal, the type of solid solution and interfacial intermetallics depended on the metallurgical reactions between the filler metals and base metals. The interfacial intermetallics were Fe2Ti＋Ni3Ti＋NiTi2, TiFe, and Cu2Ti＋CuTi＋CuTi2 in the joints welded with Ni, V, and Cu filler metals, respectively. The tensile strengths of the joints were dependent on the hardness of the interfacial intermetallics. The joint welded with Ag filler metal had the highest tensile strength, which is about 310 MPa.

Effect of porosity on mechanical properties of porous tantalum scaffolds produced by electron beam powder bed fusion

The effect of porosity on compressive,bending,and tensile properties of the porous tantalum scaffolds fabricated by electron beam powder bed fusion(EB-PBF)was investigated.The porous tantalum scaffolds with porosity from 69%to 77.8%were obtained by varying the designed porosity and adjusting the processing parameters.It is found that the pores and unfused powder decrease with the increase of deposited energy density.The decrease of porosity leads to an improvement in mechanical properties.The relevancy between compressive/bending/tensile yield strength and relative density can be described appropriately by exponential model,while the relationship between elastic modulus and relative density is in good agreement with the Gibson-Ashby model.All the porous tantalum scaffolds exhibit good ductility in compressive,bending and tensile tests.No fragmentation of struts is observed during the compression process,but cracks are formed on the strut surface after 90°bending,mainly due to the high sensibility to defects caused by the oxide.

Milliampere He^2+ beam generator using a compact GHz ECRIS

Multi-charged helium ion beam He2＋ is useful for helium accelerator to obtain a higher energy with lower cost and for deuterium accelerator to avoid neutron activation during machine commissioning. An attempt to generate milliampere multi-charged helium He2＋ ion beam with a 2.45 GHz electron cyclotron resonance ion source （ECRIS） was tested recently. A design using a specfic permanent magnet 2.45 GHz ECRIS （PMECRIS） source （ERCIS） is reported and the He2~ beam production ability is described. With this source, we produced a total helium beam of 40 mA at 40 kV with 180 W of net microwave power and a gas flow of less than 0.5 seem. At steady state the He2＋ beam intensity is 4.4 rnA, that being the fraction of multi-charged he- lium ion beam is at approximately 11%.

Effect of Cu content on the glass forming ability of Cu-Zr-Ti system studied by ion beam mixing

Based on the Cu-Zr-Ti ternary phase diagram,four sets of Cu-Zr-Ti multilayered films with various compositions of Cu20Zr36Ti44,Cu36Zr31Ti33,Cu49Zr24Ti27,and Cu67Zr16Ti17 were prepared and then the ion beam mixing was carried out.It turned out that the increase of Cu content doesn't always have a positive effect on the glass forming ability.The glass forming ability of Cu49Zr24Ti27 was degraded due to the appearance of a Cs Cl-type B2 structure Cu Zr phase in the eutectic region.The experimental observations justify the existence of the Cu Zr phase under the non-equilibrium condition.Possible formation mechanisms for the crystalline phase were also discussed in terms of the atomic collision theory.