Laser powder bed fusion(LPBF)is a widely used and well-developed approach in additive manufacturing.To meet the high material performance requirements of fourth-generation nuclear power reactors,the combination of LPB...Laser powder bed fusion(LPBF)is a widely used and well-developed approach in additive manufacturing.To meet the high material performance requirements of fourth-generation nuclear power reactors,the combination of LPBF processing with oxide dispersion strengthening(ODS)is currently of interest for the design and development of new materials.In this approach,nanoscale Y_(2)O_(3)particles are dispersed into the feeding powders to produce LPBF-ODS materials.Oxygen exposure and the introduction of oxygen into the solvation cell during LPBF are usually considered as detrimental processes that are impossible to eliminate completely.However,our understanding of these unavoidable processes is still limited.In this study,we developed a new LPBF-ODS design approach based on in situ oxygen content regulation during the LPBF process.The oxygen content of the environmental chamber was artificially adjusted using an online monitoring system to activate reactions between oxygen and the metallic elements for the in situ formation of dispersed oxide particles.Four batches of LPBF 304 L stainless steel samples were successfully processed under different oxygen levels to investigate the reinforcement effect of in situ chemical alloying.The results show that dispersed oxide particles were formed with an average nanoscale size of approximately 46 nm through the LPBF in situ alloying approach.The increase in the number density of oxide particles to 11.4 particles∕μm^(2)as the oxygen content increased played a role in refining and stabilizing the cellular structure.The yield strength of the in situ alloyed ODS material was enhanced(to up to~675 MPa)while its ductility was not significantly degraded(elongation of up to~39%).These tensile properties are competitive within the ranges reported for ODS alloys prepared by mechanical alloying.The main mechanisms for yield strength enhancement through interactions between nanoscale oxide particles and dislocation entanglement cells were analyzed.This study provides a new approach for the future preparation of high-performance LPBF-ODS alloys.展开更多
350 keV He^(+) ions were injected into laser powder bed fusion(LPBF)-processed 304L stainless steel and traditional rolled 304L stainless steel with a flux of 1×10^(17) ions/cm^(2) at room temperature,followed by...350 keV He^(+) ions were injected into laser powder bed fusion(LPBF)-processed 304L stainless steel and traditional rolled 304L stainless steel with a flux of 1×10^(17) ions/cm^(2) at room temperature,followed by annealing at 750℃ for 10,100,and 300 h,respectively.The results showed that material swelling due to helium bubble coarsening was almost not observed in either the LPBF or rolled samples after 10 h of annealing duration.Rapid coarsening and swelling of bubbles occurred in the rolled samples,but only moderate bubble growth occurred in the LPBF sample after annealing for 100 h.After annealing for 300 h,the helium bubbles in both samples tended to grow steadily.For 10 h of annealing,the irradiated samples were in a disequilibrium state,and the apparent activation energy(E^(act))calculated by the Arrhenius model determined that helium atoms tended to diffuse through the displacement mechanism,and helium bubbles grew under the migration and coalescence(MC)mechanism.With annealing times over 100 h,the high-density dislocations and nano-oxide particles in the LPBF sample still had a strong trapping effect on the movement and growth of helium bubbles.After annealing for 300 h,the cellular subgrains in the LPBF sample decomposed,and the nano-oxide particles had no trapping effect on the helium bubbles.At this time,the dislocation structure played a primary role in suppressing the growth of helium bubbles,and the radiation resistance of the LPBF sample remained superior to that of the rolled samples.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U22B2067 and 52073176)。
文摘Laser powder bed fusion(LPBF)is a widely used and well-developed approach in additive manufacturing.To meet the high material performance requirements of fourth-generation nuclear power reactors,the combination of LPBF processing with oxide dispersion strengthening(ODS)is currently of interest for the design and development of new materials.In this approach,nanoscale Y_(2)O_(3)particles are dispersed into the feeding powders to produce LPBF-ODS materials.Oxygen exposure and the introduction of oxygen into the solvation cell during LPBF are usually considered as detrimental processes that are impossible to eliminate completely.However,our understanding of these unavoidable processes is still limited.In this study,we developed a new LPBF-ODS design approach based on in situ oxygen content regulation during the LPBF process.The oxygen content of the environmental chamber was artificially adjusted using an online monitoring system to activate reactions between oxygen and the metallic elements for the in situ formation of dispersed oxide particles.Four batches of LPBF 304 L stainless steel samples were successfully processed under different oxygen levels to investigate the reinforcement effect of in situ chemical alloying.The results show that dispersed oxide particles were formed with an average nanoscale size of approximately 46 nm through the LPBF in situ alloying approach.The increase in the number density of oxide particles to 11.4 particles∕μm^(2)as the oxygen content increased played a role in refining and stabilizing the cellular structure.The yield strength of the in situ alloyed ODS material was enhanced(to up to~675 MPa)while its ductility was not significantly degraded(elongation of up to~39%).These tensile properties are competitive within the ranges reported for ODS alloys prepared by mechanical alloying.The main mechanisms for yield strength enhancement through interactions between nanoscale oxide particles and dislocation entanglement cells were analyzed.This study provides a new approach for the future preparation of high-performance LPBF-ODS alloys.
基金supported by the National Natural Science Foundation of China(Nos.U22B2067 and 52073176).
文摘350 keV He^(+) ions were injected into laser powder bed fusion(LPBF)-processed 304L stainless steel and traditional rolled 304L stainless steel with a flux of 1×10^(17) ions/cm^(2) at room temperature,followed by annealing at 750℃ for 10,100,and 300 h,respectively.The results showed that material swelling due to helium bubble coarsening was almost not observed in either the LPBF or rolled samples after 10 h of annealing duration.Rapid coarsening and swelling of bubbles occurred in the rolled samples,but only moderate bubble growth occurred in the LPBF sample after annealing for 100 h.After annealing for 300 h,the helium bubbles in both samples tended to grow steadily.For 10 h of annealing,the irradiated samples were in a disequilibrium state,and the apparent activation energy(E^(act))calculated by the Arrhenius model determined that helium atoms tended to diffuse through the displacement mechanism,and helium bubbles grew under the migration and coalescence(MC)mechanism.With annealing times over 100 h,the high-density dislocations and nano-oxide particles in the LPBF sample still had a strong trapping effect on the movement and growth of helium bubbles.After annealing for 300 h,the cellular subgrains in the LPBF sample decomposed,and the nano-oxide particles had no trapping effect on the helium bubbles.At this time,the dislocation structure played a primary role in suppressing the growth of helium bubbles,and the radiation resistance of the LPBF sample remained superior to that of the rolled samples.
