Oxide dispersion strengthened （ODS） steels can be used as the structural materials in the future fusion reactors and the fuel cladding materials in the advanced fission reactors. However, the weldability of ODS stee...Oxide dispersion strengthened （ODS） steels can be used as the structural materials in the future fusion reactors and the fuel cladding materials in the advanced fission reactors. However, the weldability of ODS steels is a severe problem. In the present study, defect-free joints of the 15Cr-ODS ferritic steel were achieved by friction stir welding at different rotation speeds. The recrystallization, hardness and tensile properties are highly related with the rotation speed of the stir tool. The higher rotation speed results in coarser grains in the top SZ, while the grain size exhibits more complicated relation with the rotation speed in the SZ center. The joint welded at 250 rpm exhibits a maximum tensile strength of 974 MPa that reaches about 84% of that of the base metal.展开更多
In this study, 2219-T87 aluminum alloys were butt welded by the double-pass tungsten inert gas arc welding process. And the softening behavior of fusion zone（FZ） and heat-affected zone（HAZ） was evaluated with the ...In this study, 2219-T87 aluminum alloys were butt welded by the double-pass tungsten inert gas arc welding process. And the softening behavior of fusion zone（FZ） and heat-affected zone（HAZ） was evaluated with the analysis of welding temperature field, grain size, alloying element distribution and precipitates evolution. Results show that the two FZs are almost the weakest regions in the joint, where the microhardness value is 76 and 78 HV, respectively. Microhardness of the HAZ generally grows along with increasing distance from fusion line except a valley value at the distance of about 4.5 mm. The mean grain size of two FZs is about 74.4 and 79.2 lm, whereas 41.5, 44.9 and 43.4 lm for the two measured HAZs and base metal（BM）, respectively. There is about 60.4% and 54.2% Cu consumed in the coarse whitish particles of FZs that have little strengthening effect, while the percentage is about 24.6% of BM that is almost the same as HAZ. A large number of strengthening phases h0 distribute dispersively in BM, whereas hardly any precipitates exist in FZ and HAZ adjacent to FZ. So the coarsening of grain size, reduction and segregation of alloying element content, and the precipitate evolution are regarded as the main causes of softening in FZ, while the precipitate evolution is the main factor of softening in HAZ.展开更多
This study investigates the cryogenic tensile properties and fracture behavior of fiction stir welded and post-weld heat-treated joints of 32Mn-7Cr-1Mo-0.3N steel. Cryogenic brittle fracture, which occurred in the as-...This study investigates the cryogenic tensile properties and fracture behavior of fiction stir welded and post-weld heat-treated joints of 32Mn-7Cr-1Mo-0.3N steel. Cryogenic brittle fracture, which occurred in the as-welded joint, is related to the residual particles that contain tungsten in the joint band structure. Post-weld water toughening resulted in the cryogenic intergranular brittleness of the joint, which is related to the non-equilibrium segregation of solute atoms during the post-weld water toughening. Annealing at 55OC for 30rain can effectively inhibit the cryogenic intergranular brittleness of the post- weld water-toughened joint. The yield strength, ultimate tensile strength, and uniform elongation of the annealed joint are approximately 95%, 87%, and 94% of the corresponding data of the base metal.展开更多
基金support of the National Magnet Confinement Fusion Energy Research Program(Grand No.2013GB108001)
文摘Oxide dispersion strengthened （ODS） steels can be used as the structural materials in the future fusion reactors and the fuel cladding materials in the advanced fission reactors. However, the weldability of ODS steels is a severe problem. In the present study, defect-free joints of the 15Cr-ODS ferritic steel were achieved by friction stir welding at different rotation speeds. The recrystallization, hardness and tensile properties are highly related with the rotation speed of the stir tool. The higher rotation speed results in coarser grains in the top SZ, while the grain size exhibits more complicated relation with the rotation speed in the SZ center. The joint welded at 250 rpm exhibits a maximum tensile strength of 974 MPa that reaches about 84% of that of the base metal.
基金supported by the National Key Basic Research Program of China under Grant No.2012CB619503
文摘In this study, 2219-T87 aluminum alloys were butt welded by the double-pass tungsten inert gas arc welding process. And the softening behavior of fusion zone（FZ） and heat-affected zone（HAZ） was evaluated with the analysis of welding temperature field, grain size, alloying element distribution and precipitates evolution. Results show that the two FZs are almost the weakest regions in the joint, where the microhardness value is 76 and 78 HV, respectively. Microhardness of the HAZ generally grows along with increasing distance from fusion line except a valley value at the distance of about 4.5 mm. The mean grain size of two FZs is about 74.4 and 79.2 lm, whereas 41.5, 44.9 and 43.4 lm for the two measured HAZs and base metal（BM）, respectively. There is about 60.4% and 54.2% Cu consumed in the coarse whitish particles of FZs that have little strengthening effect, while the percentage is about 24.6% of BM that is almost the same as HAZ. A large number of strengthening phases h0 distribute dispersively in BM, whereas hardly any precipitates exist in FZ and HAZ adjacent to FZ. So the coarsening of grain size, reduction and segregation of alloying element content, and the precipitate evolution are regarded as the main causes of softening in FZ, while the precipitate evolution is the main factor of softening in HAZ.
基金Financial support by State Key Lab of Advanced Welding and Joining,Harbin Institute of Technology
文摘This study investigates the cryogenic tensile properties and fracture behavior of fiction stir welded and post-weld heat-treated joints of 32Mn-7Cr-1Mo-0.3N steel. Cryogenic brittle fracture, which occurred in the as-welded joint, is related to the residual particles that contain tungsten in the joint band structure. Post-weld water toughening resulted in the cryogenic intergranular brittleness of the joint, which is related to the non-equilibrium segregation of solute atoms during the post-weld water toughening. Annealing at 55OC for 30rain can effectively inhibit the cryogenic intergranular brittleness of the post- weld water-toughened joint. The yield strength, ultimate tensile strength, and uniform elongation of the annealed joint are approximately 95%, 87%, and 94% of the corresponding data of the base metal.
