北京钢研高纳科技股份有限公司

In view of the deformation problem of metal foam core and pin during the test of the metal foam ultra-high speed centrifugal ventilator assembled in aero-engines,the strength calculation of the metal foam core and pin structure of the centrifugal ventilator was carried out.The results show that insufficient structural strength of the metal foam core is the main cause of the deformation of the metal foam core and pin.To improve the structural strength of the centrifugal ventilator,the yield strength and elastic modulus of the core were enhanced by optimizing the alloy composition of the metal foam core material and strengthening its preparation process.Simulation calculations and test verifications were conducted on the improved metal foam core.The results indicate that the stress of the improved metal foam core and pin is significantly reduced,and the service life of the metal foam ultra-high speed centrifugal ventilator with the improved core can satisfy the operational requirements of aero-engine.

The effects of two-stage aging time at 720 ℃ and 620 ℃ on the η phase and γ'/γ'' phase of GH4706 superalloy were studied using optical microscopy， scanning electron microscopy， etc. The room temperature strength， impact， and creep rupture life of the material were tested under different aging times. The results showed that the room temperature strength changed little at 720 ℃ and 620 ℃ two-stage aging with increasing aging time， the room temperature impact performance decreased， and the creep rupture fracture time gradually increased； Meanwhile， the quantity and size of the η phase gradually increased with the increase of aging time， and the shape of the η phase gradually changed from strip to block， while the morphology of the γ ´/γ´´ phase changed relatively little， and the γ´/γ´´ phase coarsened with the increase of aging time； By analyzing the evolution laws of γ '/γ'' phases and η phases of alloy under different aging time conditions， it was revealed that appropriate coarsening of γ´/γ´´ phases can improve the room temperature strength and high temperature durability under different aging time conditions， while the coarsening of η phases can significantly reduce the room temperature impact performance and strength of matrix， but can obviously improve the high temperature durability.

An investigation is conducted into the mechanisms by which varying levels of phosphorus （P） affect the high-temperature properties，particularly the stress rupture properties，of GH4738 alloy. This is achieved through the use of scanning electron microscopy（SEM），transmission electron microscopy（TEM），electron backscatter diffraction（EBSD）analysis，and molecular dynamics simulations. Stress rupture experiments reveals that the optimal stress rupture properties of GH4738 alloy are obtained when the phosphorus content is increased from 0.004%（mass fraction） to 0.0091%. Beyond this range，an increase in phosphorus content lead to a decline in stress rupture properties. Further microstructural analysis and molecular dynamics simulations demonstrates that phosphorus tends to segregate at grain boundaries，enhancing the cohesion force and bonding energy of these boundaries. Additionally，phosphorus interacts with carbides at grain boundaries to influence stress rupture properties. Specifically，as the phosphorus content increases from 0.004% to 0.0091%，M23C6 carbides at grain boundaries gradually transition from a small，discrete distribution to a discontinuous chain-like distribution. This enhances the pinning effect on dislocations，effectively suppressing their movement and resulting in improved stress rupture properties. However，when the phosphorus content reaches a certain threshold，such as 0.019%，the morphology of M23C6 carbides at grain boundaries changes to a plate-like shape，leading to a decrease in stress rupture properties.

The new GH4198 nickel based super-alloy is a key material for high-performance aviation engine hot end components,and its turning machinability has a significant impact on surface quality and service performance.The turning experiments based on single factor method are conducted and the influence of turning parameters on turning force,turning temperature,and surface roughness is studied.The experimental results show that within the range of experimental parameters,both turning force and turning temperature increase continuously with the in-crease of turning parameters.Among them,the factor that has the greatest impact on turning force is turning depth,with a maximum turning force of 685.2 N;The factor that has the greatest impact on turning temperature is turning speed,with a maximum turning temperature of 484.8℃;The feed rate has the greatest impact on surface rough-ness,with a minimum surface roughness of 0.346 μm.Therefore,during rough machining,a turning speed of v=130 m/min,a feed rate of f=0.14 mm/r,and a turning depth of ap=0.8 mm can be selected to achieve efficient material removal.During precision machining,a turning speed of v=90 m/min,a feed rate of f=0.06 mm/r,and a turning depth of ap=0.3 mm can be selected to improve surface quality,providing a theoretical basis for the pro-cessing of the new material GH4198.

The high alloying degree of GH4151 nickel-based superalloy leads to cracks and crystal mixing defects in the billet process,which significantly reduces the material utilization rate.Meanwhile,the grain size of GH4151 is more sen-sitive to the temperature and time of solid solution treatment.Using vacuum induction smelting(VIM)+electric slag re-melting(ESR)+vacuum arc remelting(VAR)triple smelting GH4151 ingot,after homogenization billet preparation intoϕ200 mm round bar,through the metallurgical microscope(OM),scanning electron microscope(SEM)and back scatter-ing electron diffraction(EBSD)characterization,system analyzed the bar typical microscopic tissue characteristics,heart crack and edge mixing defect formation mechanism,and combining the experiment,optimize the solid heat treatment pro-cess.The results demonstrate that,after standard heat treatment,the GH4151 bar exhibits a uniform equiaxed fine-grained structure,with an average grain size of 14.7 μm.A high density of secondary γ'precipitates(100 nm-200 nm)is uniformly distributed within the grains,significantly enhancing the high-temperature performance.The formation of cen-tral cracks is attributed to coarse grains and Laves phase precipitates induced by adiabatic temperature rise,with crack propagation predominantly guided by primary γ'precipitates and MC carbides.The edge abnormal grain structures are pri-marily caused by insufficient deformation,leading to incomplete recrystallization.Solution treatment experiments indicate that the optimal sub-solvus treatment condition is 1 120℃-1 150 ℃ for 90 min-240 min,effectively suppressing abnormal grain growth.