Commercial nanosized alumina and titania particles were selected as raw materials to prepare the blended slurry with composition of A1203-13%TiO2 （mass fraction）, which were reconstituted into micrometer-sized granu...Commercial nanosized alumina and titania particles were selected as raw materials to prepare the blended slurry with composition of A1203-13%TiO2 （mass fraction）, which were reconstituted into micrometer-sized granules by spray drying, subsequently sintering at different temperatures to form nanostructured feedstock for thermal spraying, and then A1203-13%TiO2 nanocoatings were deposited by plasma spraying. The evolution of morphology, microstructure, and phase transformation of the agglomerated powder and as-sprayed coatings were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that A1203 retains the same a phase as the raw material during sintering, while TiO2 changes from anatase to futile. During plasma spraying, some a-A1203 phases solidify to form metastable y-A1203, and the volume fraction of a-A1203 decreases as CPSP increases. However, peaks of the TiO2 phase are not observed from the as-sprayed coatings except for the coatings sprayed at the lower CPSP. As the CPSP increases, nanostructured TiO2 is dissolved easily in y-A1203 or z-A1203＇TiO2 phase. After heat treatment, y-A1203 in the coatings transforms to a-A1203, and rutile is precipitated.展开更多
This work systematically investigates the densification,microstructure evolution and the attainment of high strength-ductility in Ti-13Nb-13Zr-2Ta alloy processed by laser powder bed fusion(LPBF).A narrow and viable p...This work systematically investigates the densification,microstructure evolution and the attainment of high strength-ductility in Ti-13Nb-13Zr-2Ta alloy processed by laser powder bed fusion(LPBF).A narrow and viable process window(P_(laser power)=175 W,v_(scanning speed)=1000 mm/s,h_(scanning distance)=0.1 mm and d_(layer thickness)=0.03 mm)was accordingly determined and the relative density of Ti-13Nb-13Zr-2Ta alloy reaches 99.76%.The depth of molten pool increases gradually with the increase of energy density,and the relationship between the depth of molten pool and energy density has been quantitatively described.Three types ofα′martensites with average grain width less than 3μm can be observed in the LPBF-fabricated Ti-13Nb-13Zr-2Ta alloys,attributed to the significantly high cooling rate and remelting process.The fine grain size,high density dislocations,nanotwins,ordered oxygen complexes andα+α″heterostructure all contributed to the high strength(1037.75±25.18 MPa)and ductility(20.32%±1.39%)of LPBF-fabricated Ti-13Nb-13Zr-2Ta alloy in this work.展开更多
The molten pool size,residual stress and defects of H13 steel prepared by laser powder bed fusion(LPBF)under various process parameters were investigated.The residual stress range for both defective and crack-free sam...The molten pool size,residual stress and defects of H13 steel prepared by laser powder bed fusion(LPBF)under various process parameters were investigated.The residual stress range for both defective and crack-free samples was 1420-1550 MPa.High scanning speeds led to incomplete melting defects,whereas low scanning speeds resulted in crack defects.Additionally,finite element simulation was employed to elucidate the defect formation mechanisms in H13 steel produced via LPBF process.We developed optimal parameters for LPBF of H13 steel,achieving a relative density of 99.8% in the prepared samples.The analysis indicated that crack formation primarily resulted from stress concentration at grain boundaries.Furthermore,the samples comprised α-Fe phase and a minor amount of retained γ-Fe austenite phase,facilitated by high solidification rates and low residual stress.In conclusion,optimizing LPBF manufacturing process for H13 steel requires considering both the impact of parameters on defect formation and the influence of the forming process on martensite and retained austenite.展开更多
基金Projects(51072045,51102074)supported by the National Natural Science Foundation of China
文摘Commercial nanosized alumina and titania particles were selected as raw materials to prepare the blended slurry with composition of A1203-13%TiO2 （mass fraction）, which were reconstituted into micrometer-sized granules by spray drying, subsequently sintering at different temperatures to form nanostructured feedstock for thermal spraying, and then A1203-13%TiO2 nanocoatings were deposited by plasma spraying. The evolution of morphology, microstructure, and phase transformation of the agglomerated powder and as-sprayed coatings were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that A1203 retains the same a phase as the raw material during sintering, while TiO2 changes from anatase to futile. During plasma spraying, some a-A1203 phases solidify to form metastable y-A1203, and the volume fraction of a-A1203 decreases as CPSP increases. However, peaks of the TiO2 phase are not observed from the as-sprayed coatings except for the coatings sprayed at the lower CPSP. As the CPSP increases, nanostructured TiO2 is dissolved easily in y-A1203 or z-A1203＇TiO2 phase. After heat treatment, y-A1203 in the coatings transforms to a-A1203, and rutile is precipitated.
基金supported by the National Natural Science Foundation of China(Grant No.52205140)the Outstanding Youth Foundation of Hunan Province(Grant No.2023JJ20041)+1 种基金the Science and Technology Innovation Program of Hunan Province(2023RC3241)the Research Foundation of Education Bureau of Hunan Province(Grant No.22A0216).
文摘This work systematically investigates the densification,microstructure evolution and the attainment of high strength-ductility in Ti-13Nb-13Zr-2Ta alloy processed by laser powder bed fusion(LPBF).A narrow and viable process window(P_(laser power)=175 W,v_(scanning speed)=1000 mm/s,h_(scanning distance)=0.1 mm and d_(layer thickness)=0.03 mm)was accordingly determined and the relative density of Ti-13Nb-13Zr-2Ta alloy reaches 99.76%.The depth of molten pool increases gradually with the increase of energy density,and the relationship between the depth of molten pool and energy density has been quantitatively described.Three types ofα′martensites with average grain width less than 3μm can be observed in the LPBF-fabricated Ti-13Nb-13Zr-2Ta alloys,attributed to the significantly high cooling rate and remelting process.The fine grain size,high density dislocations,nanotwins,ordered oxygen complexes andα+α″heterostructure all contributed to the high strength(1037.75±25.18 MPa)and ductility(20.32%±1.39%)of LPBF-fabricated Ti-13Nb-13Zr-2Ta alloy in this work.
基金support from National Natural Science Foundation of China(Nos.52434009 and 52404351).
文摘The molten pool size,residual stress and defects of H13 steel prepared by laser powder bed fusion(LPBF)under various process parameters were investigated.The residual stress range for both defective and crack-free samples was 1420-1550 MPa.High scanning speeds led to incomplete melting defects,whereas low scanning speeds resulted in crack defects.Additionally,finite element simulation was employed to elucidate the defect formation mechanisms in H13 steel produced via LPBF process.We developed optimal parameters for LPBF of H13 steel,achieving a relative density of 99.8% in the prepared samples.The analysis indicated that crack formation primarily resulted from stress concentration at grain boundaries.Furthermore,the samples comprised α-Fe phase and a minor amount of retained γ-Fe austenite phase,facilitated by high solidification rates and low residual stress.In conclusion,optimizing LPBF manufacturing process for H13 steel requires considering both the impact of parameters on defect formation and the influence of the forming process on martensite and retained austenite.
