Recently,multi-pass caliber rolling has been shown to be effective for Mg alloys.This study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate th...Recently,multi-pass caliber rolling has been shown to be effective for Mg alloys.This study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate the strength-ductility relationship.This annealing gave rise to different trends in mechanical properties depending on the temperature regime.Low-temperature annealing(T≤473 K)exhibited a typical trade-off relationship,where an increase in annealing temperature resulted in increased ductility but decreased strength and hardness.Such a heat treatment did not degrade the high strength-ductility balance of the caliber-rolled alloy,suggesting that the mechanical properties could be tailored for different potential applications.In contrast,high-temperature annealing(T>473 K)caused a simultaneous deterioration in strength,hardness,and ductility with increasing annealing temperature.These differences are discussed in terms of the varying microstructural features under the different investigated annealing regimes.展开更多
A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation processes.The present study enhanced strength and ductility of AZ31 Mg alloy simultaneously through the application...A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation processes.The present study enhanced strength and ductility of AZ31 Mg alloy simultaneously through the application of caliber rolling.The improving trends in tensile properties were interpreted with various caliber-rolling strains.The oval/circular-shaped calibers imposed a high plastic strain at the center of crosssection,leading to effective grain refinement to submicron scale.This work also confirmed the texture randomizing effect of caliber rolling.Such microstructural evolutions gave rise to the fabrication of high-strength material.Moreover,the caliber-rolled AZ31 Mg alloys exhibited an improvement in ductility as compared to the as-received sheet-rolled material.This was discussed in terms of activation of non-basal slip systems and suppression of mechanical twinning.This study successfully proved the possibility of caliber rolling to produce a bulk Mg rod with enhanced tensile properties.展开更多
Bimetallic additively manufactured structures(BAMSs)can replace traditionally-fabricated functionallygraded-components through fusion welding processes and can eliminate locally-deteriorated mechanical properties aris...Bimetallic additively manufactured structures(BAMSs)can replace traditionally-fabricated functionallygraded-components through fusion welding processes and can eliminate locally-deteriorated mechanical properties arising from post-processing.The present work fabricates a BAMS by sequentially depositing the austenitic stainless-steel and Inconel625 using a gas-metal-arc-welding(GMAW)-based wire+arc additive manufacturing(WAAM)system.Elemental mapping shows a smooth compositional transition at the interface without any segregation.Both materials being the face-center-cubic(FCC)austenite,the electron backscattered diffraction(EBSD)analysis of the interface shows the smooth and cross-interfacecrystallographic growth of long-elongated grains in the<001>direction.The hardness values were within the range of 220-240 HV for both materials without a large deviation at the interface.Due to the controlled thermal history,mechanical testing yielded a consistent result with the ultimate tensile strength and elongation of 600 MPa and 40%,respectively,with the failure location on the stainless-steel side.This study demonstrates that WAAM has the potential to fabricate BAMS with controlled properties.展开更多
Wire+arc additive manufacturing(WAAM)is considered an innovative technology that can change the manufacturing landscape in the near future.WAAM offers the benefits of inexpensive initial system setup and a high deposi...Wire+arc additive manufacturing(WAAM)is considered an innovative technology that can change the manufacturing landscape in the near future.WAAM offers the benefits of inexpensive initial system setup and a high deposition rate for fabricating medium-and large-sized parts such as die-casting tools.In this study,AISI H13 tool steel,a popular die-casting tool metal,is manufactured by cold metal transfer(CMT)-based WAAM and is then comprehensively analyzed for its microstructural and mechanical properties.Location-dependent phase combinations are observed,which could be explained by nonequilibrium thermal cycles that resulted from the layer-by-layer stacking mechanism used in WAAM.In addition,remelting and reheating of the layers reduces welding anomalies(e.g.,pores and voids).The metallurgical characteristics of the H13 strongly correlate with the mechanical properties.The combinations of phases at different locations of the additively manufactured part exhibit a periodic microhardness profile.Martensite,Retained Austenite,Ferrite,and Carbide phases are found in combination at different locations of the part based on the part’s temperature distribution during additive deposition.Moreover,the tensile properties at elevated temperatures(23℃,300℃,and 600℃)are comparable to those from other WAAM and additive manufacturing(AM)processes.The X-ray diffraction results verify that the microstructural stability of the fabricated parts at high temperatures would allow them to be used in high temperatures.展开更多
基金This work was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)through GCRC-SOP(No.2011-0030013).
文摘Recently,multi-pass caliber rolling has been shown to be effective for Mg alloys.This study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate the strength-ductility relationship.This annealing gave rise to different trends in mechanical properties depending on the temperature regime.Low-temperature annealing(T≤473 K)exhibited a typical trade-off relationship,where an increase in annealing temperature resulted in increased ductility but decreased strength and hardness.Such a heat treatment did not degrade the high strength-ductility balance of the caliber-rolled alloy,suggesting that the mechanical properties could be tailored for different potential applications.In contrast,high-temperature annealing(T>473 K)caused a simultaneous deterioration in strength,hardness,and ductility with increasing annealing temperature.These differences are discussed in terms of the varying microstructural features under the different investigated annealing regimes.
基金This work was supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.2018R1C1B6002068).
文摘A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation processes.The present study enhanced strength and ductility of AZ31 Mg alloy simultaneously through the application of caliber rolling.The improving trends in tensile properties were interpreted with various caliber-rolling strains.The oval/circular-shaped calibers imposed a high plastic strain at the center of crosssection,leading to effective grain refinement to submicron scale.This work also confirmed the texture randomizing effect of caliber rolling.Such microstructural evolutions gave rise to the fabrication of high-strength material.Moreover,the caliber-rolled AZ31 Mg alloys exhibited an improvement in ductility as compared to the as-received sheet-rolled material.This was discussed in terms of activation of non-basal slip systems and suppression of mechanical twinning.This study successfully proved the possibility of caliber rolling to produce a bulk Mg rod with enhanced tensile properties.
基金This study has been conducted with the support of the Korea Institute of Industrial Technology as a project on the development of metal 3D printing materials and process optimization technology for medium-and large-sized transportation part mold manufacturing(KITECH JE200008).
文摘Bimetallic additively manufactured structures(BAMSs)can replace traditionally-fabricated functionallygraded-components through fusion welding processes and can eliminate locally-deteriorated mechanical properties arising from post-processing.The present work fabricates a BAMS by sequentially depositing the austenitic stainless-steel and Inconel625 using a gas-metal-arc-welding(GMAW)-based wire+arc additive manufacturing(WAAM)system.Elemental mapping shows a smooth compositional transition at the interface without any segregation.Both materials being the face-center-cubic(FCC)austenite,the electron backscattered diffraction(EBSD)analysis of the interface shows the smooth and cross-interfacecrystallographic growth of long-elongated grains in the<001>direction.The hardness values were within the range of 220-240 HV for both materials without a large deviation at the interface.Due to the controlled thermal history,mechanical testing yielded a consistent result with the ultimate tensile strength and elongation of 600 MPa and 40%,respectively,with the failure location on the stainless-steel side.This study demonstrates that WAAM has the potential to fabricate BAMS with controlled properties.
基金support of the Korea Institute of Industrial Technology as a project on the development of metal 3D printing materials and process optimization technology for medium-and large-sized transportation part mold manufacturing(KITECH JE200008)。
文摘Wire+arc additive manufacturing(WAAM)is considered an innovative technology that can change the manufacturing landscape in the near future.WAAM offers the benefits of inexpensive initial system setup and a high deposition rate for fabricating medium-and large-sized parts such as die-casting tools.In this study,AISI H13 tool steel,a popular die-casting tool metal,is manufactured by cold metal transfer(CMT)-based WAAM and is then comprehensively analyzed for its microstructural and mechanical properties.Location-dependent phase combinations are observed,which could be explained by nonequilibrium thermal cycles that resulted from the layer-by-layer stacking mechanism used in WAAM.In addition,remelting and reheating of the layers reduces welding anomalies(e.g.,pores and voids).The metallurgical characteristics of the H13 strongly correlate with the mechanical properties.The combinations of phases at different locations of the additively manufactured part exhibit a periodic microhardness profile.Martensite,Retained Austenite,Ferrite,and Carbide phases are found in combination at different locations of the part based on the part’s temperature distribution during additive deposition.Moreover,the tensile properties at elevated temperatures(23℃,300℃,and 600℃)are comparable to those from other WAAM and additive manufacturing(AM)processes.The X-ray diffraction results verify that the microstructural stability of the fabricated parts at high temperatures would allow them to be used in high temperatures.
