A bimodal-structured Mg^(-1)5Gd binary alloy with 45%volume fraction of elongated grains and 55%of dynamically recrystallized(DRXed)grains is fabricated by the extrusion process.The precipitating behavior correlating ...A bimodal-structured Mg^(-1)5Gd binary alloy with 45%volume fraction of elongated grains and 55%of dynamically recrystallized(DRXed)grains is fabricated by the extrusion process.The precipitating behavior correlating with the evolution of mechanical properties is systematically characterized during the subsequent aging treatment at 200°C.The extruded alloy presents an outstanding strength with tensile yield strength of 466 MPa and ultimate tensile strength of 500 MPa at peak aging condition,while the elongation drops from 9.2%in extrusion state to 3.1%.It is found there obviously exist a rapidly decreasing range of ductility at the early stage of aging.Just during this time,the nano precipitates form preferentially at lamellar dislocation boundaries(LDBs)within the elongated grains,but there is no dense and uniform precipitation in the matrix.The results suggest that the low elongation in the aged Mg^(-1)5Gd alloy is mainly attributed to the nano precipitates prior formed at the LDBs with a high density in the elongated grains.The related mechanism has been clarified.展开更多
A conventional multi-pass rolling is designed to form different microstructures in a Mg-2Ag alloy.The relationship between microstructure and mechanical property is investigated.The result shows that twin-induced nucl...A conventional multi-pass rolling is designed to form different microstructures in a Mg-2Ag alloy.The relationship between microstructure and mechanical property is investigated.The result shows that twin-induced nucleation plays a prominent role for the dynamic recrystallization(DRX)behavior of the rolled Mg-2Ag alloys.The DRXed grains distributed around elongated grains have random orientations but gradually turn to the concentrated orientation with strong basal texture when the rolling pass increases.The yield strength and ultimate tensile strength of rolled Mg-2Ag alloy gradually increase with increasing rolling pass.The elongation of rolled sample is gradually improved when the rolling pass increases from one to three,while a significant drop of elongation shows in the four-pass rolling sample.The strong basal texture,refined grains,high-density dislocations,and Ag segregation along grain boundaries are suggested to play a prominent role for enhancing the strength of Mg-Ag alloys,while the low-density dislocations,homogeneously fine-grained microstructure,and weak texture are critical for improving the ductility.展开更多
High-energy ball milling(HEBM)combined with powder metallurgy route was used to fabricate carbon nanotube(CNT)reinforced 7055 Al composites.Two powder morphology evolution processes(HEBM-1 and HEBM-2)were designed to ...High-energy ball milling(HEBM)combined with powder metallurgy route was used to fabricate carbon nanotube(CNT)reinforced 7055 Al composites.Two powder morphology evolution processes(HEBM-1 and HEBM-2)were designed to investigate the dispersion and damage of CNTs during HEBM process.HEBM-1 evolution process involved powder fl attening,cold-welding and fracture,while HEBM-2 evolution process consisted of powder fl attening and fracture.For HEBM-1,the repetitive fracture and cold-welding process was effective for dispersing CNTs.However,the powder fl attening process in HEBM-2 was unsuccessful in dispersing CNTs due to two reasons:(1)the thickness of fl aky Al powders exceeded the critical value,and(2)the clustered CNTs embedded in fl aky Al powders could not be unravelled.Because of the broadening of D band and the appearance of a new defect-related D’band,product of I D/I G and full width half maximum of D band,rather than I D/I G,was used to evaluate the actual damage of CNTs.It indicates that the damage of CNTs was severe in powder fl attening and fracture stages,while the damage of CNTs was small in powder cold-welding stage.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.52171121,51971151,52201131,52201132,52171055 and 52071220)Liao Ning Xingliao Program(XLYC1907083)+1 种基金Natural Science Foundation of Liaoning Province of China(2022-NLTS-18-01)the Open Foundation of Key Laboratory of Superlight Materials&Surface Technology of Ministry of Education(HEU10202205).
文摘A bimodal-structured Mg^(-1)5Gd binary alloy with 45%volume fraction of elongated grains and 55%of dynamically recrystallized(DRXed)grains is fabricated by the extrusion process.The precipitating behavior correlating with the evolution of mechanical properties is systematically characterized during the subsequent aging treatment at 200°C.The extruded alloy presents an outstanding strength with tensile yield strength of 466 MPa and ultimate tensile strength of 500 MPa at peak aging condition,while the elongation drops from 9.2%in extrusion state to 3.1%.It is found there obviously exist a rapidly decreasing range of ductility at the early stage of aging.Just during this time,the nano precipitates form preferentially at lamellar dislocation boundaries(LDBs)within the elongated grains,but there is no dense and uniform precipitation in the matrix.The results suggest that the low elongation in the aged Mg^(-1)5Gd alloy is mainly attributed to the nano precipitates prior formed at the LDBs with a high density in the elongated grains.The related mechanism has been clarified.
基金supported by the National Natural Science Foundation of China(Nos.52171121,51971151,and 51971053)the Liao Ning XingLiao Program(No.XLYC1907083)+4 种基金the Science Research Project of Liaoning Province Education Department(No.LQ2019002)the Fundamental Research Funds for the Central Universities(No.N2202020)the Science Research Project of Liaoning Province Education Department(No.LJ2020015)Natural Science Foundation of Liaoning Province of China(2022-NLTS-18-01)the Open Foundation of Key Laboratory of Superlight Materials&Surface Technology of Ministry of Education(HEU10202205).
文摘A conventional multi-pass rolling is designed to form different microstructures in a Mg-2Ag alloy.The relationship between microstructure and mechanical property is investigated.The result shows that twin-induced nucleation plays a prominent role for the dynamic recrystallization(DRX)behavior of the rolled Mg-2Ag alloys.The DRXed grains distributed around elongated grains have random orientations but gradually turn to the concentrated orientation with strong basal texture when the rolling pass increases.The yield strength and ultimate tensile strength of rolled Mg-2Ag alloy gradually increase with increasing rolling pass.The elongation of rolled sample is gradually improved when the rolling pass increases from one to three,while a significant drop of elongation shows in the four-pass rolling sample.The strong basal texture,refined grains,high-density dislocations,and Ag segregation along grain boundaries are suggested to play a prominent role for enhancing the strength of Mg-Ag alloys,while the low-density dislocations,homogeneously fine-grained microstructure,and weak texture are critical for improving the ductility.
基金supported by the Key Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-JSC015)the National Key R&D Program of China(No.2017YFB0703104)+2 种基金the Project of manned spaceflight(No.040103)the National Natural Science Foundation of China(Nos.51931009,51871215)the Youth Innovation Promotion Association CAS(No.2020197)。
文摘High-energy ball milling(HEBM)combined with powder metallurgy route was used to fabricate carbon nanotube(CNT)reinforced 7055 Al composites.Two powder morphology evolution processes(HEBM-1 and HEBM-2)were designed to investigate the dispersion and damage of CNTs during HEBM process.HEBM-1 evolution process involved powder fl attening,cold-welding and fracture,while HEBM-2 evolution process consisted of powder fl attening and fracture.For HEBM-1,the repetitive fracture and cold-welding process was effective for dispersing CNTs.However,the powder fl attening process in HEBM-2 was unsuccessful in dispersing CNTs due to two reasons:(1)the thickness of fl aky Al powders exceeded the critical value,and(2)the clustered CNTs embedded in fl aky Al powders could not be unravelled.Because of the broadening of D band and the appearance of a new defect-related D’band,product of I D/I G and full width half maximum of D band,rather than I D/I G,was used to evaluate the actual damage of CNTs.It indicates that the damage of CNTs was severe in powder fl attening and fracture stages,while the damage of CNTs was small in powder cold-welding stage.
