Primary γ'phase instead of carbides and borides plays an important role in suppressing grain growth during solution at 1433 K of Ni-based FGH98 superalloys.Results illustrate that as-fabricated FGH98 superalloy h...Primary γ'phase instead of carbides and borides plays an important role in suppressing grain growth during solution at 1433 K of Ni-based FGH98 superalloys.Results illustrate that as-fabricated FGH98 superalloy has equiaxed grain structure,and after heat treatment,grains remain equiaxed but grow larger.In order to clarify the effects of the size and volume fraction of the primaryγ'phase on the grain growth during heat treatment,a 2D cellular automata(CA)model was established based on the thermal activation and the lowest energy principle.The CA results are compared with the experimental results and show a good fit with an error less than 10%.Grain growth kinetics are depicted,and simulations in real time for various sizes and volume fractions of primaryγ'particles work out well with the Zener relation.The coefficient n value which reflects the pinning ability in Zener relation is theoretically calculated,and its minimum value is 0.23 when the radius of primaryγ'phase is 2.8μm.展开更多
Diffusion bonding(DB)with interlayers is sought-after for manufacturing high-performance turbine disks of powder metallurgy(PM)superalloys with precise and intricate inner cavity structures.Developing novel interlayer...Diffusion bonding(DB)with interlayers is sought-after for manufacturing high-performance turbine disks of powder metallurgy(PM)superalloys with precise and intricate inner cavity structures.Developing novel interlayer materials is challenging but crucial for enhancing bonding quality and joint properties.We designed a multi-interlayer composite bonding(MICB)method,employing sandwich-structured inter-layers of"BNi2/high entropy alloy(HEA)/BNi2",to join a PM superalloy FGH98.The MICB joint exhibited an ultrahigh shear strength of~1132 MPa and exceptional ductility,indicating a typical ductile fracture pattern with numerous dimples.Owing to the introduction of liquid BNi2 interlayer,initial bonding in-terfaces were eliminated and replaced by newborn grain boundaries(GBs),preventing brittle interfacial fracture.Due to the diffusion of Al/Ti/Ta from the base metals(BMs),massive orderedγ'nanoparticles also precipitated in the joint.Moreover,the addition of HEA foil reduced the stacking fault energy(SFE)of the joint and facilitated the formation of deformation twins(DTs).Thus,during the deformation process,theγ'nanoparticles,and multiple substructures like stacking faults(SFs),Lomer-Cottrell(L-C)locks,DTs,and 9R phases enhanced the work-hardening capability and strengthened the joint.Simultaneously,the multiplication and interaction of DTs induced a softening mechanism of dynamic recrystallization(DRX)during the entire deformation process and dominated when the plastic instability occurred,resulting in numerous adiabatic shear bands(ASBs)consisting ofγ/γ'nano-bands,which indicates a significant im-provement of the joint ductility.展开更多
基金financially supported by the National Natural Science Foundation of China(52005410 and 52375146)China Postdoctoral Science Foundation(2019TQ0263 and 2020M683560)the Fundamental Research Funds for the Central Universities.
基金National Major Science and Technology Project(2017-VI-0009-0079)Basic and Applied Basic Research Foundation of Guangdong Province(2020B0301030001).
文摘Primary γ'phase instead of carbides and borides plays an important role in suppressing grain growth during solution at 1433 K of Ni-based FGH98 superalloys.Results illustrate that as-fabricated FGH98 superalloy has equiaxed grain structure,and after heat treatment,grains remain equiaxed but grow larger.In order to clarify the effects of the size and volume fraction of the primaryγ'phase on the grain growth during heat treatment,a 2D cellular automata(CA)model was established based on the thermal activation and the lowest energy principle.The CA results are compared with the experimental results and show a good fit with an error less than 10%.Grain growth kinetics are depicted,and simulations in real time for various sizes and volume fractions of primaryγ'particles work out well with the Zener relation.The coefficient n value which reflects the pinning ability in Zener relation is theoretically calculated,and its minimum value is 0.23 when the radius of primaryγ'phase is 2.8μm.
基金support from the National Natural Science Foundation of China(Grant Nos.52075449,51975480,and 52222112)the Hong Kong Research Grant Council(RGC)(Grant No.21205621).
文摘Diffusion bonding(DB)with interlayers is sought-after for manufacturing high-performance turbine disks of powder metallurgy(PM)superalloys with precise and intricate inner cavity structures.Developing novel interlayer materials is challenging but crucial for enhancing bonding quality and joint properties.We designed a multi-interlayer composite bonding(MICB)method,employing sandwich-structured inter-layers of"BNi2/high entropy alloy(HEA)/BNi2",to join a PM superalloy FGH98.The MICB joint exhibited an ultrahigh shear strength of~1132 MPa and exceptional ductility,indicating a typical ductile fracture pattern with numerous dimples.Owing to the introduction of liquid BNi2 interlayer,initial bonding in-terfaces were eliminated and replaced by newborn grain boundaries(GBs),preventing brittle interfacial fracture.Due to the diffusion of Al/Ti/Ta from the base metals(BMs),massive orderedγ'nanoparticles also precipitated in the joint.Moreover,the addition of HEA foil reduced the stacking fault energy(SFE)of the joint and facilitated the formation of deformation twins(DTs).Thus,during the deformation process,theγ'nanoparticles,and multiple substructures like stacking faults(SFs),Lomer-Cottrell(L-C)locks,DTs,and 9R phases enhanced the work-hardening capability and strengthened the joint.Simultaneously,the multiplication and interaction of DTs induced a softening mechanism of dynamic recrystallization(DRX)during the entire deformation process and dominated when the plastic instability occurred,resulting in numerous adiabatic shear bands(ASBs)consisting ofγ/γ'nano-bands,which indicates a significant im-provement of the joint ductility.
