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
Investigation has been made on the causes of hot cracking in the surfacing layer of Ni_3Al basealloy by analysing the solidification process of fusion pool and the distribution of thermal stresses. The re-sults show t...Investigation has been made on the causes of hot cracking in the surfacing layer of Ni_3Al basealloy by analysing the solidification process of fusion pool and the distribution of thermal stresses. The re-sults show that the cracking is directly related to both the occurrence of eutectic phase β' (NiAI) within theinterdendritic region and high thernial stresses in the surfacing layer ,and which are caused by selecting highwelding rate. When the process of electric arc weld is changed from straight line rnovement to that along’Z’pattern,the cracking in the surfacing layer of Ni_3Al base alloy is prevented owing to being reduced of boththe cooling rate of liquid in the fusion liool and the speed of the moving heat source. Lowering the outputpower of the electric arc welding could lead to the reducing of rnelting volume of the base material ,and lowerthe arnount of iron atoms dissolving in the fusion pool ,so that the trend of the eutectic reaction within the in-terdendritic region is reduced,and which is helpful to suppress the cracking in the surfacing layer of Ni_3Albase alloy.展开更多
Al/Ni multilayer composites are produced by accumulative roll bonding process and then annealed with different temperatures and time.Macroscopic images,microstructure and mechanical properties of Al/Ni multilayer comp...Al/Ni multilayer composites are produced by accumulative roll bonding process and then annealed with different temperatures and time.Macroscopic images,microstructure and mechanical properties of Al/Ni multilayer composites are investigated.As for the macroscopic images,although there was an edge crack along the rolling direction at the third pass,the defect of composites was not serious and the forming quality of composites was relatively good.The yield strength and elongation of Al/Ni multilayer composites are improved after the annealing treatment;however,with the increase in annealing temperature and time,the yield strength and ciongation of Al/Ni multilayer composites are decreased.During the process of annealing treatment,aluminum atoms diffuse in the way of vacancy diffusion,which results in the formation of Al3Ni intermetallic phase at Al/Ni interface and Kirkendall void in the aluminum side.The content of Al3Ni intermetallic phase and Kirkenckill void would increase with the increase in annealing temperature and time.展开更多
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.
基金supported by the foundation of '863' high technology in China
文摘Investigation has been made on the causes of hot cracking in the surfacing layer of Ni_3Al basealloy by analysing the solidification process of fusion pool and the distribution of thermal stresses. The re-sults show that the cracking is directly related to both the occurrence of eutectic phase β' (NiAI) within theinterdendritic region and high thernial stresses in the surfacing layer ,and which are caused by selecting highwelding rate. When the process of electric arc weld is changed from straight line rnovement to that along’Z’pattern,the cracking in the surfacing layer of Ni_3Al base alloy is prevented owing to being reduced of boththe cooling rate of liquid in the fusion liool and the speed of the moving heat source. Lowering the outputpower of the electric arc welding could lead to the reducing of rnelting volume of the base material ,and lowerthe arnount of iron atoms dissolving in the fusion pool ,so that the trend of the eutectic reaction within the in-terdendritic region is reduced,and which is helpful to suppress the cracking in the surfacing layer of Ni_3Albase alloy.
基金This research is sponsored by the National Natural Science Foundation of China(NSFC 51605307)the Scientific Research Foundation of the Education Department of Liaoning Province,China(LGD2016020).
文摘Al/Ni multilayer composites are produced by accumulative roll bonding process and then annealed with different temperatures and time.Macroscopic images,microstructure and mechanical properties of Al/Ni multilayer composites are investigated.As for the macroscopic images,although there was an edge crack along the rolling direction at the third pass,the defect of composites was not serious and the forming quality of composites was relatively good.The yield strength and elongation of Al/Ni multilayer composites are improved after the annealing treatment;however,with the increase in annealing temperature and time,the yield strength and ciongation of Al/Ni multilayer composites are decreased.During the process of annealing treatment,aluminum atoms diffuse in the way of vacancy diffusion,which results in the formation of Al3Ni intermetallic phase at Al/Ni interface and Kirkendall void in the aluminum side.The content of Al3Ni intermetallic phase and Kirkenckill void would increase with the increase in annealing temperature and time.
