Diffusion bonding and additive manufacturing(AM)are suitable joining and manufacturing techniques for producing aluminium alloy components even with highly intricate geometries.However,the generation of aluminium oxid...Diffusion bonding and additive manufacturing(AM)are suitable joining and manufacturing techniques for producing aluminium alloy components even with highly intricate geometries.However,the generation of aluminium oxide(Al_(2)O_(3))scaling occurring on the surfaces of successively deposited aluminium layers decreases the metal-to-metal contact in extrusion-based AM applications.Al2 O3 scaling leads to poor quality of final fabricated parts and thereby achieving low bonding(joint)strength from bonded layers.In this regard,accurately predicting the minimum holding time required is essential for effectively mitigating Al_(2)O_(3)scaling,and achieving high-quality aluminium parts.This consideration involves optimising the duration of the diffusion bonding process and the consolidation pressure applied by print heads or consecutive rollers in extrusion-based AM process.There is currently neither mathematical model nor machine learning model developed for predicting the bonding time for similar or dissimilar aluminium and its alloys.Therefore,the current paper proposes both mathematical and supervised machine learning models using regression-based approach to predict the minimum holding time required to achieve sound AA7075-T6 joints at 450℃,475℃and 500℃.The mathematical model explicitly incorporates the closure of micro-voids through plastic deformation coupled with power-law creep of both AA7075-T6 and Al_(2)O_(3),as well as volume,grain boundary,and surface diffusion.Notably,the creep and plastic deformations of Al_(2)O_(3)scaling are included for the first time in any diffusion bonding model for more realistically modelling void closure.Then,the bonding time was predicted using a machine learning code in which several techniques were incorporated to robust the model i.e.feature scaling,polynomial feature expansion,regularisation and mean squared error technique.The proposed mathematical model exhibited an excellent agreement with experimental results,particularly at low pressure levels and all data points at 450℃,whereas the machine learning model predicted bonding time more accurately than the mathematical model particularly at 475℃.展开更多
Angle deviations between the two substrates during transient liquid phase （TLP） bonding single crystal superalloys cannot be avoided. In the present work, specimens have been prepared to investigate the influences o...Angle deviations between the two substrates during transient liquid phase （TLP） bonding single crystal superalloys cannot be avoided. In the present work, specimens have been prepared to investigate the influences of the various substrate orientations. It is found that the width of the non-isothermal solidification zone （NSZ） is linear with the square root of the isothermal solidification time. This suggests that the isothermal solidification process is B-diffusion controlled in different substrate orientation deviations. And also the width of the NSZ increases with increasing angle deviation, indicating that the isothermal solidification time needed in the TLP bonding increases with increasing orientation deviation between the two substrates.展开更多
The transient liquid phase(TLP)bonding of CoCuFeMnNi high entropy alloy(HEA)was studied.The TLP bonding was performed using AWS BNi-2 interlayer at 1050℃ with the TLP bonding time of 20,60,180 and 240 min.The effect ...The transient liquid phase(TLP)bonding of CoCuFeMnNi high entropy alloy(HEA)was studied.The TLP bonding was performed using AWS BNi-2 interlayer at 1050℃ with the TLP bonding time of 20,60,180 and 240 min.The effect of bonding time on the joint microstructure was characterized by SEM and EDS.Microstructural results confirmed that complete isothermal solidification occurred approximately at 240 min of bonding time.For samples bonded at 20,60 and 180 min,athermal solidification zone was formed in the bonding area which included Cr-rich boride and Mn3Si intermetallic compound.For all samples,theγsolid solution was formed in the isothermal solidification zone of the bonding zone.To evaluate the effect of TLP bonding time on mechanical properties of joints,the shear strength and micro-hardness of joints were measured.The results indicated a decrement of micro-hardness in the bonding zone and an increment of micro-hardness in the adjacent zone of joints.The minimum and maximum values of shear strength were 100 and 180 MPa for joints with the bonding time of 20 and 240 min,respectively.展开更多
The liquid-film solution-diffusion bonding of ZCuBe2.5 alloys was conducted using Cu-based alloy powders. The tensile strength of the joint is up to 318 MPa. With the increase of temperature gradient, the bonding time...The liquid-film solution-diffusion bonding of ZCuBe2.5 alloys was conducted using Cu-based alloy powders. The tensile strength of the joint is up to 318 MPa. With the increase of temperature gradient, the bonding time decreases and the interface migration velocity increases remarkably. The appropriate temperature gradient is 5-40 K/cm. Under fixed bonding time, the thickness of diffusion layer increases with the increase of temperature gradient, and this tendency becomes more remarkable with the prolonging of bonding time.展开更多
Background Enamel demineralization occurs frequently during orthodontic treatment. In this study, we evaluated the changes of the density of mutans streptococcus （MS） in plaque after bracket bonding and using fluori...Background Enamel demineralization occurs frequently during orthodontic treatment. In this study, we evaluated the changes of the density of mutans streptococcus （MS） in plaque after bracket bonding and using fluoride adhesive on maxillary incisors by real time fluorescence-quantitative polymerase chain reaction （RT-FQ PCR）.Methods The study was designed as a self-paired test. Brackets were bonded with fluoride adhesive on the left side, while non-fluoride adhesive on the right side for each patient. Plaque samples were taken from the surfaces around the brackets of four maxillary incisors before brackets bonding and after the bonding 4 weeks later. The amount of MS was measured by RT-FQ PCR. The data obtained were analyzed statistically using the SPSS 11.5 version and the alpha level was set at 0. 05 （ 2-tailed）.Results The amount of MS in plaque increased significantly after bracket bonding （ P 〈 0.01 ）, whereas no significant differences were observed among four maxillary incisors both before and after brackets bonding （P 〉 0. 05 ）, and among the incisors using and not using fluoride adhesive （ P 〉 0. 05 ）.Conclusions The increase of the density of MS in plaque after bracket bonding is one of the etiological factors for enamel demineralization in orthodontic patients. The result of this study did not support what we observed clinically that the incidence of enamel demineralization for lateral incisors was higher than that for central incisors. Using fluoride adhesive for bonding did not affect the amount of MS in plaque in our study. Further study is needed.展开更多
文摘Diffusion bonding and additive manufacturing(AM)are suitable joining and manufacturing techniques for producing aluminium alloy components even with highly intricate geometries.However,the generation of aluminium oxide(Al_(2)O_(3))scaling occurring on the surfaces of successively deposited aluminium layers decreases the metal-to-metal contact in extrusion-based AM applications.Al2 O3 scaling leads to poor quality of final fabricated parts and thereby achieving low bonding(joint)strength from bonded layers.In this regard,accurately predicting the minimum holding time required is essential for effectively mitigating Al_(2)O_(3)scaling,and achieving high-quality aluminium parts.This consideration involves optimising the duration of the diffusion bonding process and the consolidation pressure applied by print heads or consecutive rollers in extrusion-based AM process.There is currently neither mathematical model nor machine learning model developed for predicting the bonding time for similar or dissimilar aluminium and its alloys.Therefore,the current paper proposes both mathematical and supervised machine learning models using regression-based approach to predict the minimum holding time required to achieve sound AA7075-T6 joints at 450℃,475℃and 500℃.The mathematical model explicitly incorporates the closure of micro-voids through plastic deformation coupled with power-law creep of both AA7075-T6 and Al_(2)O_(3),as well as volume,grain boundary,and surface diffusion.Notably,the creep and plastic deformations of Al_(2)O_(3)scaling are included for the first time in any diffusion bonding model for more realistically modelling void closure.Then,the bonding time was predicted using a machine learning code in which several techniques were incorporated to robust the model i.e.feature scaling,polynomial feature expansion,regularisation and mean squared error technique.The proposed mathematical model exhibited an excellent agreement with experimental results,particularly at low pressure levels and all data points at 450℃,whereas the machine learning model predicted bonding time more accurately than the mathematical model particularly at 475℃.
基金financially supported by the National Basic Research Program (973 Program) of China under Grant Nos. 2010CB631200 and 2010CB631206the National Natural Science Foundation of China (NSFC) under Grant Nos. 50971124, 50904059, 51071165 and 51204156
文摘Angle deviations between the two substrates during transient liquid phase （TLP） bonding single crystal superalloys cannot be avoided. In the present work, specimens have been prepared to investigate the influences of the various substrate orientations. It is found that the width of the non-isothermal solidification zone （NSZ） is linear with the square root of the isothermal solidification time. This suggests that the isothermal solidification process is B-diffusion controlled in different substrate orientation deviations. And also the width of the NSZ increases with increasing angle deviation, indicating that the isothermal solidification time needed in the TLP bonding increases with increasing orientation deviation between the two substrates.
文摘The transient liquid phase(TLP)bonding of CoCuFeMnNi high entropy alloy(HEA)was studied.The TLP bonding was performed using AWS BNi-2 interlayer at 1050℃ with the TLP bonding time of 20,60,180 and 240 min.The effect of bonding time on the joint microstructure was characterized by SEM and EDS.Microstructural results confirmed that complete isothermal solidification occurred approximately at 240 min of bonding time.For samples bonded at 20,60 and 180 min,athermal solidification zone was formed in the bonding area which included Cr-rich boride and Mn3Si intermetallic compound.For all samples,theγsolid solution was formed in the isothermal solidification zone of the bonding zone.To evaluate the effect of TLP bonding time on mechanical properties of joints,the shear strength and micro-hardness of joints were measured.The results indicated a decrement of micro-hardness in the bonding zone and an increment of micro-hardness in the adjacent zone of joints.The minimum and maximum values of shear strength were 100 and 180 MPa for joints with the bonding time of 20 and 240 min,respectively.
文摘The liquid-film solution-diffusion bonding of ZCuBe2.5 alloys was conducted using Cu-based alloy powders. The tensile strength of the joint is up to 318 MPa. With the increase of temperature gradient, the bonding time decreases and the interface migration velocity increases remarkably. The appropriate temperature gradient is 5-40 K/cm. Under fixed bonding time, the thickness of diffusion layer increases with the increase of temperature gradient, and this tendency becomes more remarkable with the prolonging of bonding time.
文摘Background Enamel demineralization occurs frequently during orthodontic treatment. In this study, we evaluated the changes of the density of mutans streptococcus （MS） in plaque after bracket bonding and using fluoride adhesive on maxillary incisors by real time fluorescence-quantitative polymerase chain reaction （RT-FQ PCR）.Methods The study was designed as a self-paired test. Brackets were bonded with fluoride adhesive on the left side, while non-fluoride adhesive on the right side for each patient. Plaque samples were taken from the surfaces around the brackets of four maxillary incisors before brackets bonding and after the bonding 4 weeks later. The amount of MS was measured by RT-FQ PCR. The data obtained were analyzed statistically using the SPSS 11.5 version and the alpha level was set at 0. 05 （ 2-tailed）.Results The amount of MS in plaque increased significantly after bracket bonding （ P 〈 0.01 ）, whereas no significant differences were observed among four maxillary incisors both before and after brackets bonding （P 〉 0. 05 ）, and among the incisors using and not using fluoride adhesive （ P 〉 0. 05 ）.Conclusions The increase of the density of MS in plaque after bracket bonding is one of the etiological factors for enamel demineralization in orthodontic patients. The result of this study did not support what we observed clinically that the incidence of enamel demineralization for lateral incisors was higher than that for central incisors. Using fluoride adhesive for bonding did not affect the amount of MS in plaque in our study. Further study is needed.
