Transient liquid phase(TLP)bonding is a promising process for the joining and repairing of nickel-base superalloys.One of the most important parameters in TLP bonding is the bonding time required for suf-ficient isoth...Transient liquid phase(TLP)bonding is a promising process for the joining and repairing of nickel-base superalloys.One of the most important parameters in TLP bonding is the bonding time required for suf-ficient isothermal solidification which prevents the formation of undesirable precipitated phases.In the present work,the effect of bonding time on the microstructure,type,and evolution of precipitates in the non-isothermal solidified zone(NSZ)and their effect on micro-mechanical properties were systemat-ically investigated using multi-scale tests in TLP bonded Mar-M247 superalloy joints with Ni-15.2Cr-3.74B interlayer at 1230℃.For a bonding time of 5 min,dual-phase M_(23)(C,B)_(6)-γ/γ’(where M is a mix-ture of Hf,Ta,Cr,and Ni)with eutectic configuration was formed in NSZ.With the increase in bonding time,the evolution of NSZ microstructure can be summed up as eutectic M_(23)(C,B)_(6)-γ/γ’,semi-striping dual-phase M_(23)(C,B)_(6)-γ/γ’,discontinuously striping M_(23)(C,B)_(6)-γ/γ’,followed by the disintegration of NSZ.As the NSZ counterpart,the isothermal solidified zone(ISZ)is mainly composed ofγ/γ’.Ac-companied by the dissolution of M_(23)(C,B)_(6) in the centerline,the proportion of the ISZ increases greatly until the joints are completely occupied by ISZ.Finally,a bamboo-like structure with domain size of-100μm was formed in the joint centerline,along withγ’reorganized themselves all into cubic shapes and distributed homogeneously.Mechanical property tests demonstrated that in comparison to samples with longer bonding time,the NSZ of the shortest bonding time(5 min)has the highest strength and a subsequent decrease in strength was observed with prolonging the bonding time and post-bond heat treatment.Furthermore,possible solidification/transformation path,segregation behavior,and formation mechanism of NSZ/ISZ evolution were discussed.展开更多
Abscisic acid(ABA)is a key phytohormone that mediates environmental stress responses.Vitamin C,or L-ascorbic acid(AsA),is the most abundant antioxidant protecting against stress damage in plants.How the ABA and AsA si...Abscisic acid(ABA)is a key phytohormone that mediates environmental stress responses.Vitamin C,or L-ascorbic acid(AsA),is the most abundant antioxidant protecting against stress damage in plants.How the ABA and AsA signaling pathways interact in stress responses remains elusive.In this study,we characterized the role of a previously unidentified gene,PTPN(PTP-like Nucleotidase)in plant drought tolerance.In Arabidopsis,(AtPTPN was expressed in multiple tissues and upregulated by ABA and drought treatments.Loss-of-function mutants oiAtPTPN were hyposensitive to ABA but hypersensitive to drought stresses,whereas plants with enhanced expression AtPTPN showed opposite phenotypes to.Overexpression of maize PTPN(ZmPTPN)promoted,while knockdown oiZmPTPN inhibited plant drought tolerance,indicating conserved and positive roles of PTPN in plant drought tolerance.We found that both AtPTPN and ZmPTPN release Pi by hydrolyzing GDP/GMP/dGMP/IMP/dIMP,and that AtPTPN positively regulated AsA production via endogenous Pi content control.Consistently,overexpression of VTC2,the rate-limiting synthetic enzyme in AsA biosynthesis,promoted AsA production and plant drought tolerance,and these effects were largely dependent on AtPTPN activity.Furthermore,we demonstrated that the heat shock transcription factor HSFA6a directly binds the AtPTPN promoter and activates AtPTPN expression.Genetic analyses showed that AtPTPN is required for HSFA6a to regulate ABA and drought responses.Taken together,our data indicate that PTPN-mediated crosstalk between the ABA signaling and AsA biosynthesis pathways positively controls plant drought tolerance.展开更多
基金supported by the National Natural Science Foundation of China(No.52125101)the Basic and Applied Basic Research Major Program of Guangdong Province,China(Grant No.2021B0301030003)the Jihua Laboratory(Project No.X210141TL210).
文摘Transient liquid phase(TLP)bonding is a promising process for the joining and repairing of nickel-base superalloys.One of the most important parameters in TLP bonding is the bonding time required for suf-ficient isothermal solidification which prevents the formation of undesirable precipitated phases.In the present work,the effect of bonding time on the microstructure,type,and evolution of precipitates in the non-isothermal solidified zone(NSZ)and their effect on micro-mechanical properties were systemat-ically investigated using multi-scale tests in TLP bonded Mar-M247 superalloy joints with Ni-15.2Cr-3.74B interlayer at 1230℃.For a bonding time of 5 min,dual-phase M_(23)(C,B)_(6)-γ/γ’(where M is a mix-ture of Hf,Ta,Cr,and Ni)with eutectic configuration was formed in NSZ.With the increase in bonding time,the evolution of NSZ microstructure can be summed up as eutectic M_(23)(C,B)_(6)-γ/γ’,semi-striping dual-phase M_(23)(C,B)_(6)-γ/γ’,discontinuously striping M_(23)(C,B)_(6)-γ/γ’,followed by the disintegration of NSZ.As the NSZ counterpart,the isothermal solidified zone(ISZ)is mainly composed ofγ/γ’.Ac-companied by the dissolution of M_(23)(C,B)_(6) in the centerline,the proportion of the ISZ increases greatly until the joints are completely occupied by ISZ.Finally,a bamboo-like structure with domain size of-100μm was formed in the joint centerline,along withγ’reorganized themselves all into cubic shapes and distributed homogeneously.Mechanical property tests demonstrated that in comparison to samples with longer bonding time,the NSZ of the shortest bonding time(5 min)has the highest strength and a subsequent decrease in strength was observed with prolonging the bonding time and post-bond heat treatment.Furthermore,possible solidification/transformation path,segregation behavior,and formation mechanism of NSZ/ISZ evolution were discussed.
基金the National Key Research and Development Program of China(2016YFD0100600)the National Natural Science Foundation of China(31971954)+1 种基金the Thousand Talents Plan of China and the Fundamental Research Funds for the Central Universities of China(2662015PY170)partly supported by the open funds of the National Key Laboratory of Crop Genetic Improvement.
文摘Abscisic acid(ABA)is a key phytohormone that mediates environmental stress responses.Vitamin C,or L-ascorbic acid(AsA),is the most abundant antioxidant protecting against stress damage in plants.How the ABA and AsA signaling pathways interact in stress responses remains elusive.In this study,we characterized the role of a previously unidentified gene,PTPN(PTP-like Nucleotidase)in plant drought tolerance.In Arabidopsis,(AtPTPN was expressed in multiple tissues and upregulated by ABA and drought treatments.Loss-of-function mutants oiAtPTPN were hyposensitive to ABA but hypersensitive to drought stresses,whereas plants with enhanced expression AtPTPN showed opposite phenotypes to.Overexpression of maize PTPN(ZmPTPN)promoted,while knockdown oiZmPTPN inhibited plant drought tolerance,indicating conserved and positive roles of PTPN in plant drought tolerance.We found that both AtPTPN and ZmPTPN release Pi by hydrolyzing GDP/GMP/dGMP/IMP/dIMP,and that AtPTPN positively regulated AsA production via endogenous Pi content control.Consistently,overexpression of VTC2,the rate-limiting synthetic enzyme in AsA biosynthesis,promoted AsA production and plant drought tolerance,and these effects were largely dependent on AtPTPN activity.Furthermore,we demonstrated that the heat shock transcription factor HSFA6a directly binds the AtPTPN promoter and activates AtPTPN expression.Genetic analyses showed that AtPTPN is required for HSFA6a to regulate ABA and drought responses.Taken together,our data indicate that PTPN-mediated crosstalk between the ABA signaling and AsA biosynthesis pathways positively controls plant drought tolerance.
