Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated ...Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated on the Mg alloy substrate,and then Sn_(3.0)Ag_(0.5)Cu(SAC 305)solder was utilized to facilitate the joining of AZ31 Mg/6061 Al through ultrasonic-assisted soldering.We investigated the impactof Al_(2)O_(3)nano sol content in the coating on microstructure evolution,IMCs formation,and mechanical properties.Results indicated that theNi-Al_(2)O_(3)composite coating effectively suppressed the Mg-Sn reaction,thereby preventing the formation of Mg_(2)Sn IMC and significantlyenhancing joint strength.In joints with a Ni-Al_(2)O_(3)composite coating containing 50 mL/L Al_(2)O_(3)nano sol,no Mg_(2)Sn IMC was detectedafter 50 min of holding at 260℃,achieving a maximum shear strength of approximately 67.2 MPa.Increasing the Al_(2)O_(3)concentrationfurther expanded the soldering process window.For the joint with Ni-Al_(2)O_(3)(100 mL/L Al_(2)O_(3)nano sol)composite coating held at 260℃for 70 min,the coating was dissolved to a thickness of about 5.8μm,but no Mg_(2)Sn IMC was observed.The Ni-based solid solution formednear the coating/solder interface was strengthened,leading to fractures occurring within the SAC solder,and the maximum shear strengthfurther increased to 73.9 MPa.The strengthening mechanism of the joints facilitated by using the Ni-Al_(2)O_(3)composite coating was revealedby comparing with pure Ni-assisted joints.Therefore,employing a Ni-Al_(2)O_(3)composite coating as a barrier layer represents a promisingstrategy for inhibiting IMC formation during the joining of dissimilar metals.展开更多
A double-layered W/Mg structure is expected to be a new generation of nuclear radiation shielding material.The tungsten heavy alloy(W90)and AZ31B Mg alloy were firstly bonded by ultrasonic-assisted soldering using pur...A double-layered W/Mg structure is expected to be a new generation of nuclear radiation shielding material.The tungsten heavy alloy(W90)and AZ31B Mg alloy were firstly bonded by ultrasonic-assisted soldering using pure Sn and Sn-Al filler metal in an atmospheric environment.The influence of ultrasonication time on the microstructure and mechanical properties of the joint was investigated.The typical microstructure of the W90/Sn/Mg joint was W90/Mg_(2)Sn+Sn/Mg_(2)Sn layer/Mg.As the ultrasonication time increased from 2 s to 10 s,the joint width reduced and the thickness of the Mg_(2)Sn layer increased.The shear strength of the joint firstly increased,then flattened,and finally decreased.The joint strength reached the maximum value of 10.5 MPa.The fracture position of the joint changed from the W90/filler metal interface to the Mg_(2)Sn layer.The addition of Al in Sn resulted in the formation of the Al4 W phase at the W/Sn-1Al interface.The W/filler metal interface changed from the semi-coherent interface to the coherent interface and the joint strength increased.As the ultrasonication time was 6 s,the shear strength W90/Sn-1Al/Mg joint reached the maximum value of 24.6 MPa and the joint fractured at two positions:W90/filler metal interface and filler metal.With the further increase of ultrasonication time,the joint strength decreased and the joint fractured in the Mg_(2)Sn layer.展开更多
The microstructure of primary Mg_(2)Si and the interface of Mg_(2)Si/α-Mg modified by Sn and Sb elements in an as-cast Mg-5Sn-2Si-1.5Al-1Zn-0.8Sb(wt.%) alloy were investigated.In the primary Mg_(2)Si phase not only t...The microstructure of primary Mg_(2)Si and the interface of Mg_(2)Si/α-Mg modified by Sn and Sb elements in an as-cast Mg-5Sn-2Si-1.5Al-1Zn-0.8Sb(wt.%) alloy were investigated.In the primary Mg_(2)Si phase not only the Si atoms but also the Mg atoms could be substituted by Sn and Sb atoms,resulting in the slightly reduced lattice constant a of 0.627 nm.An OR of Mg_(2)Si phase and α-Mg in the form of[001]Mg_(2)Si‖[01■1]α,(220)Mg_(2)Si‖(0■12)αwas discovered.Between primary Mg_(2)Si phase and α-Mg matrix two transitional nano-particle layers were formed.In the rim region of primary Mg_(2)Si particle,Mg_(2)Sn precipitates sizing from 5 nm to 50 nm were observed.Adjacent to the boundary of primary Mg_(2)Si particle,luxuriant columnar crystals of primary Mg_(2)Sn phase with width of about 25 nm and length of about100 nm were distributed on the α-Mg matrix.The lattice constant of the Mg_(2)Sn precipitate in primary Mg_(2)Si particle was about 0.756 nm.Three ORs between Mg_(2)Sn and Mg_(2)Si were found,in which the Mg_(2)Sn precipitates had strong bonding interfaces with Mg_(2)Si phase.Three new minor ORs between Mg_(2)Sn phase and α-Mg were found.The lattice constant of primary Mg_(2)Sn phase was enlarged to 0.813 nm owing to the solution of Sn and Sb atoms.Primary Mg_(2)Sn had edge-to-edge interfaces with α-Mg.Therefore,the primary Mg_(2)Si particle and α-Mg were united and the interfacial adhesion was improved by the two nano-particles layers of Mg_(2)Sn phase.展开更多
Magnesium-based materials have been regarded as promising candidates for large-scale,high-efficiency thermoelectric applications,owing to their excellent dimensionless figure of merit,high abundance,and low cost.In th...Magnesium-based materials have been regarded as promising candidates for large-scale,high-efficiency thermoelectric applications,owing to their excellent dimensionless figure of merit,high abundance,and low cost.In this review,we comprehensively summarize the recent advances of Mg-based thermoelectrics,including Mg_(2)X(X=Si,Ge,Sn),Mg3(Sb,Bi)_(2),andα-MgAgSb,from both material and device level.Their electrical and thermal transport properties are first elucidated based on the crystallographic characteristics,band structures,and phonon dispersions.We then review the optimization strategies towards higher thermoelectric performance,as well as the device applications of Mg-based thermoelectric materials and the related engineering issues.By highlighting the challenges and possible solutions in the end,this review intends to offer perspectives on the future research work to further enhance the performance of Mg-based materials for practical applications.展开更多
Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joi...Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joint performance of Mg/Al.In this study,AZ31 Mg alloy with/without a nickel(Ni)coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu(SAC)filler.The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated.The Ni coating layer had a significant effect on formation of the Mg_(2)Sn IMC and the mechanical properties of Mg/Al joints.The blocky Mg_(2)Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer.The content of the Mg_(2)Sn IMC increased with increasing soldering temperature,but the joint strength decreased.The joint without a Ni coating layer fractured at the blocky Mg_(2)Sn IMC in the solder,and the maximum shear strength was 32.2 MPa.By pre-plating Ni on the Mg substrate,formation of the blocky Mg_(2)Sn IMC was inhibited in the soldering temperature range 240–280℃and the joint strength increased.However,when the soldering temperature increased to 310℃,the blocky Mg_(2)Sn IMC precipitated again in the solder.Transmission electron microscopy showed that some nano-sized Mg_(2)Sn IMC and the(Cu,Ni)_(6)Sn_(5)phase formed in the Mg(Ni)/SAC/Al joint soldered at 280℃,indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280℃.The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280℃,which was 80.7%higher than that of the Mg/SAC/Al joint,and the joint was broken at the Mg(Ni)/SAC interface.Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.展开更多
The Mg-Sn alloys,with basal or prismatic Mg_(2)Sn laths,were employed to reveal the effect of precipitate orientation on twinning behavior quantitatively.The Mg-5wt.%Sn alloys with basal or prismatic Mg_(2)Sn were com...The Mg-Sn alloys,with basal or prismatic Mg_(2)Sn laths,were employed to reveal the effect of precipitate orientation on twinning behavior quantitatively.The Mg-5wt.%Sn alloys with basal or prismatic Mg_(2)Sn were compressed to study the twinning behaviors.Subsequently,an Orowan strengthening model was developed to quantitatively investigate the critical resolved shear stress(CRSS)increment of precipitates on twinning.The results revealed that the prismatic precipitates hindered the transfer and growth of tensile twins more effectively compared with the basal precipitates.The decreased proportion of tensile twins containing prismatic Mg_(2)Sn might be attributed to a larger CRSS increment for tensile twins compared with that for basal precipitates.The obvious decreased twinning transfer in the alloy with prismatic Mg_(2)Sn could be due to its higher geometrically necessary dislocation and enhanced CRSS of tensile twins.Notably,the prismatic precipitates have a better hindering effect on tensile twins during compression.展开更多
基金support from the National Natural Science Foundation of China(grant numbers 52275385 and U2167216).
文摘Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated on the Mg alloy substrate,and then Sn_(3.0)Ag_(0.5)Cu(SAC 305)solder was utilized to facilitate the joining of AZ31 Mg/6061 Al through ultrasonic-assisted soldering.We investigated the impactof Al_(2)O_(3)nano sol content in the coating on microstructure evolution,IMCs formation,and mechanical properties.Results indicated that theNi-Al_(2)O_(3)composite coating effectively suppressed the Mg-Sn reaction,thereby preventing the formation of Mg_(2)Sn IMC and significantlyenhancing joint strength.In joints with a Ni-Al_(2)O_(3)composite coating containing 50 mL/L Al_(2)O_(3)nano sol,no Mg_(2)Sn IMC was detectedafter 50 min of holding at 260℃,achieving a maximum shear strength of approximately 67.2 MPa.Increasing the Al_(2)O_(3)concentrationfurther expanded the soldering process window.For the joint with Ni-Al_(2)O_(3)(100 mL/L Al_(2)O_(3)nano sol)composite coating held at 260℃for 70 min,the coating was dissolved to a thickness of about 5.8μm,but no Mg_(2)Sn IMC was observed.The Ni-based solid solution formednear the coating/solder interface was strengthened,leading to fractures occurring within the SAC solder,and the maximum shear strengthfurther increased to 73.9 MPa.The strengthening mechanism of the joints facilitated by using the Ni-Al_(2)O_(3)composite coating was revealedby comparing with pure Ni-assisted joints.Therefore,employing a Ni-Al_(2)O_(3)composite coating as a barrier layer represents a promisingstrategy for inhibiting IMC formation during the joining of dissimilar metals.
基金supported by the National Natural Science Foundation of China(nos.52105330 and 52175307)the Natural Science Foundation of Shandong Province(no.ZR2020QE175)the Taishan Scholars Foundation of Shandong Province(no.tsqn201812128).
文摘A double-layered W/Mg structure is expected to be a new generation of nuclear radiation shielding material.The tungsten heavy alloy(W90)and AZ31B Mg alloy were firstly bonded by ultrasonic-assisted soldering using pure Sn and Sn-Al filler metal in an atmospheric environment.The influence of ultrasonication time on the microstructure and mechanical properties of the joint was investigated.The typical microstructure of the W90/Sn/Mg joint was W90/Mg_(2)Sn+Sn/Mg_(2)Sn layer/Mg.As the ultrasonication time increased from 2 s to 10 s,the joint width reduced and the thickness of the Mg_(2)Sn layer increased.The shear strength of the joint firstly increased,then flattened,and finally decreased.The joint strength reached the maximum value of 10.5 MPa.The fracture position of the joint changed from the W90/filler metal interface to the Mg_(2)Sn layer.The addition of Al in Sn resulted in the formation of the Al4 W phase at the W/Sn-1Al interface.The W/filler metal interface changed from the semi-coherent interface to the coherent interface and the joint strength increased.As the ultrasonication time was 6 s,the shear strength W90/Sn-1Al/Mg joint reached the maximum value of 24.6 MPa and the joint fractured at two positions:W90/filler metal interface and filler metal.With the further increase of ultrasonication time,the joint strength decreased and the joint fractured in the Mg_(2)Sn layer.
基金supported by the National Natural Science Foundation of China [51571086]Research Fund for Doctoral Program of Henan Polytechnic University [B2015-14]。
文摘The microstructure of primary Mg_(2)Si and the interface of Mg_(2)Si/α-Mg modified by Sn and Sb elements in an as-cast Mg-5Sn-2Si-1.5Al-1Zn-0.8Sb(wt.%) alloy were investigated.In the primary Mg_(2)Si phase not only the Si atoms but also the Mg atoms could be substituted by Sn and Sb atoms,resulting in the slightly reduced lattice constant a of 0.627 nm.An OR of Mg_(2)Si phase and α-Mg in the form of[001]Mg_(2)Si‖[01■1]α,(220)Mg_(2)Si‖(0■12)αwas discovered.Between primary Mg_(2)Si phase and α-Mg matrix two transitional nano-particle layers were formed.In the rim region of primary Mg_(2)Si particle,Mg_(2)Sn precipitates sizing from 5 nm to 50 nm were observed.Adjacent to the boundary of primary Mg_(2)Si particle,luxuriant columnar crystals of primary Mg_(2)Sn phase with width of about 25 nm and length of about100 nm were distributed on the α-Mg matrix.The lattice constant of the Mg_(2)Sn precipitate in primary Mg_(2)Si particle was about 0.756 nm.Three ORs between Mg_(2)Sn and Mg_(2)Si were found,in which the Mg_(2)Sn precipitates had strong bonding interfaces with Mg_(2)Si phase.Three new minor ORs between Mg_(2)Sn phase and α-Mg were found.The lattice constant of primary Mg_(2)Sn phase was enlarged to 0.813 nm owing to the solution of Sn and Sb atoms.Primary Mg_(2)Sn had edge-to-edge interfaces with α-Mg.Therefore,the primary Mg_(2)Si particle and α-Mg were united and the interfacial adhesion was improved by the two nano-particles layers of Mg_(2)Sn phase.
基金financial support from the National Natural Science Foundation of China(Grant Nos.52125103,52071041,12104071,11874356,U21A2054)。
文摘Magnesium-based materials have been regarded as promising candidates for large-scale,high-efficiency thermoelectric applications,owing to their excellent dimensionless figure of merit,high abundance,and low cost.In this review,we comprehensively summarize the recent advances of Mg-based thermoelectrics,including Mg_(2)X(X=Si,Ge,Sn),Mg3(Sb,Bi)_(2),andα-MgAgSb,from both material and device level.Their electrical and thermal transport properties are first elucidated based on the crystallographic characteristics,band structures,and phonon dispersions.We then review the optimization strategies towards higher thermoelectric performance,as well as the device applications of Mg-based thermoelectric materials and the related engineering issues.By highlighting the challenges and possible solutions in the end,this review intends to offer perspectives on the future research work to further enhance the performance of Mg-based materials for practical applications.
基金financial support from the National Natural Science Foundation of China(grant numbers 52275385 and U2167216)the Sichuan Province Science and Technology Support Program(grant number 2022YFG0086)。
文摘Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joint performance of Mg/Al.In this study,AZ31 Mg alloy with/without a nickel(Ni)coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu(SAC)filler.The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated.The Ni coating layer had a significant effect on formation of the Mg_(2)Sn IMC and the mechanical properties of Mg/Al joints.The blocky Mg_(2)Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer.The content of the Mg_(2)Sn IMC increased with increasing soldering temperature,but the joint strength decreased.The joint without a Ni coating layer fractured at the blocky Mg_(2)Sn IMC in the solder,and the maximum shear strength was 32.2 MPa.By pre-plating Ni on the Mg substrate,formation of the blocky Mg_(2)Sn IMC was inhibited in the soldering temperature range 240–280℃and the joint strength increased.However,when the soldering temperature increased to 310℃,the blocky Mg_(2)Sn IMC precipitated again in the solder.Transmission electron microscopy showed that some nano-sized Mg_(2)Sn IMC and the(Cu,Ni)_(6)Sn_(5)phase formed in the Mg(Ni)/SAC/Al joint soldered at 280℃,indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280℃.The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280℃,which was 80.7%higher than that of the Mg/SAC/Al joint,and the joint was broken at the Mg(Ni)/SAC interface.Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.
基金National Natural Science Foundation of China(Nos.52004227,U22A20187,52201106)the China Postdoctoral Science Foundation(No.2020M683240)+1 种基金the Key Area Research and Development Program of Guangdong ProvinceChina(No.2020B090924002)。
文摘The Mg-Sn alloys,with basal or prismatic Mg_(2)Sn laths,were employed to reveal the effect of precipitate orientation on twinning behavior quantitatively.The Mg-5wt.%Sn alloys with basal or prismatic Mg_(2)Sn were compressed to study the twinning behaviors.Subsequently,an Orowan strengthening model was developed to quantitatively investigate the critical resolved shear stress(CRSS)increment of precipitates on twinning.The results revealed that the prismatic precipitates hindered the transfer and growth of tensile twins more effectively compared with the basal precipitates.The decreased proportion of tensile twins containing prismatic Mg_(2)Sn might be attributed to a larger CRSS increment for tensile twins compared with that for basal precipitates.The obvious decreased twinning transfer in the alloy with prismatic Mg_(2)Sn could be due to its higher geometrically necessary dislocation and enhanced CRSS of tensile twins.Notably,the prismatic precipitates have a better hindering effect on tensile twins during compression.
