Al5A06 sheets by large cold plastic deformation usually have high strength but low plasticity,i.e.weak strength-plasticity matching,which may lead to their poor fatigue property.In this study,annealing treat-ments are...Al5A06 sheets by large cold plastic deformation usually have high strength but low plasticity,i.e.weak strength-plasticity matching,which may lead to their poor fatigue property.In this study,annealing treat-ments are applied on cold rotary forged Al5A06 sheets to regulate strength-plasticity matching and im-prove fatigue properties.The microstructures,tensile mechanical properties and fatigue properties un-der different annealing parameters were analyzed.The abnormal grain growth mechanism of cold rotary forged Al5A06 sheets during 300℃ annealing treatment was investigated,and the fatigue failure mech-anism of Al5A06 sheets with different annealing temperatures was also investigated.The abnormal grain growth during 300℃ annealing treatment is mainly due to the asynchronous recrystallization behavior with low recrystallization driving force,which leads to the early recrystallized regions directly absorb-ing adjacent grains along134crystal direction.The cold rotary forged Al5A06 sheets after 250℃-2 h annealing treatment exhibit the best fatigue property,which is mainly because the optimum strength-plasticity matching brings about coordinate plastic deformation throughout most grains,and the effective dislocation movement between adjacent grains can delay the appearance of strain localization and ac-commodate continuous fatigue cyclic loading.展开更多
Al7075 sheets are widely used in aerospace industry and their higher strength-plasticity collaborative improvement requirement is urgent.In this study,the microstructure inheriting the evolution and me-chanical proper...Al7075 sheets are widely used in aerospace industry and their higher strength-plasticity collaborative improvement requirement is urgent.In this study,the microstructure inheriting the evolution and me-chanical properties of Al7075 sheets during multidirectional rotary forging(MRF)and T6 heat treatment are analyzed.The results show that the average grain size exhibits near-parabolic evolution with increas-ing MRF deformation amount.MRF20%+T6(20%MRF deformation amount+T6)condition possesses the largest grain size of 72.6μm,and its abnormal grain growth mechanism is that the medium deformation energy and high deformation heterogeneity in MRF20%deformed grains could cause asynchronous re-crystallization behavior during T6 heat treatment,and the grains with comparatively higher deformation energy get recrystallized firstly and devour adjacent grains along preferred011or223misorientation axis.MRF70%+T6 condition possesses the finest grain size of 14.2μm,and its fine grain inheriting mech-anism is that the uniformly high deformation energy in MRF70%deformed grains causes uniformly rapid recrystallization,and rapidly recrystallized grains effectively suppress grain boundary motion from adja-cent grains.With increasing MRF deformation amount,tensile strength and elongation values both exhibit near-antiparabolic evolution.MRF70%+T6 condition possesses the largest tensile strength(563 MPa)and elongation(17.73%),which increases by 8.27%and 80.55%compared to as-annealed+T6(MRF0%+T6)condition(tensile strength is 520 MPa and elongation is 9.82%),respectively.The strength-plasticity col-laborative improvement is mainly because the combination of effectively inherited fine grains,refined inclusion particles,and uniformly distributed fineη’particles after T6 heat treatment could promote smooth dislocation movement and coordinated slip behavior in most matrix grains,which contributes to the delay of stress localization and strength-plasticity collaborative improvement.展开更多
In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,met...In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,metallographic examination,and hardness test,the properties and causes of the cracks are discussed.The results indicate that the cracking type is intergranular brittle cracking,occurring during the forging stage.Furthermore,the recrystallization at the crack site is found to be incomplete,which is attributed to the low deformation temperature.展开更多
Ti-47Al-2Nb-2Cr-0.4（W, Mo） （mole fraction, %） alloy ingot fabricated using vacuum consumable melting was containerless near-isothermally forged, and the high temperature forgeability, microstructure and tensile pr...Ti-47Al-2Nb-2Cr-0.4（W, Mo） （mole fraction, %） alloy ingot fabricated using vacuum consumable melting was containerless near-isothermally forged, and the high temperature forgeability, microstructure and tensile properties were investigated. The results show that the TiAl ingot exhibits good heat workability during containerless near-isothermally forging process, and there are not evident cracks on the surface of as-forged TiAl pancake with a total deformation degree of 60%. The microstructure of the TiAl ingot appears to be typical nearly-lamellar（NL）, comprising a great amount of lamellar colonies （α2＋γ） and a few equiaxed γ grains. After near-isothermally forging, the as-forged pancake shows primarily fine equiaxed γ grains with an average grain size of 20 μm and some broken lamellar pieces, and some bent lamellas still exist in the hard-deformation zone. Tensile tests at room temperature show that ultimate tensile strength increases from 433 MPa to 573 MPa after forging due to grain refinement effect.展开更多
The microstructural evolution and tensile properties of a forged Ti−42Al−5Mn alloy subjected to different heat treatments were studied.The results showed that,when the forged alloy was aged at 800℃ for 24 h,the inter...The microstructural evolution and tensile properties of a forged Ti−42Al−5Mn alloy subjected to different heat treatments were studied.The results showed that,when the forged alloy was aged at 800℃ for 24 h,the interlamellar spacing(λ)andγgrain size at colony boundaries are generally coarsened.Whereas,when the alloy was first annealed at 1300℃ and then aged at 800℃ for 24 h,this coarsening of related microstructures appears less pronounced.The suggested annealing temperatures for the forged Ti−42Al−5Mn alloy are in the range of 1250−1300℃.It was found that,on the condition of the same annealing system,both the strength and ductility were improved as the aging temperature changed from 1000 to 800℃.The secondary precipitatedβo(β_(o,sec))at colony boundaries could be responsible for improving the strength,and theγphase at colony boundaries with the grain size about 6μm might be one of the main reasons for the better ductility.展开更多
The dynamic recrystallization behavior of microalloyed forged steel was investigated with a compression test in the temperature range of 1 223-1 473 K and a strain rate of 0. 01-5 s^-1. Activation energy was calculate...The dynamic recrystallization behavior of microalloyed forged steel was investigated with a compression test in the temperature range of 1 223-1 473 K and a strain rate of 0. 01-5 s^-1. Activation energy was calculated to be 305.9 kJ/mol by regression analysis. Modeling equations were developed to represent the dynamic recrystallization volume fraction and grain size. Parameters of the modeling equations were determined as a function of the Zener-Hollomon parameter. The developed modeling equation will be combined with finite element modeling to predict microstructural change during the hot forging processing.展开更多
Transmission electron microscopy(TEM),scanning electron microscopy(SEM),hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu...Transmission electron microscopy(TEM),scanning electron microscopy(SEM),hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy.The results show that the alloy exhibits splendid mechanical properties with an ultimate tensile strength of504MPa and an elongation of10.1%after aging at170°C for16h.With tensile testing temperature increasing to150°C,the strength of the alloy declines slightly to483MPa.Then,the strength drops quickly when temperature reaches over200°C.The high strength of the alloy in peak-aged condition is caused by a considerable amount ofθ'and AlMgSiCu(Q)precipitates.The relatively stable mechanical properties tested below150°C are mainly ascribed to the stability ofθ'precipitates.The growth ofθ'and Q precipitates and the generation ofθphase lead to a rapid drop of the strength when temperature is over150°C.展开更多
This paper investigated the high cycle fatigue behavior of a forged Mg-7Gd-5Y-1Nd-0.5Zr alloy with different stress concentration factor(Kt),under different stress ratio(R),and along different loading direction.The sm...This paper investigated the high cycle fatigue behavior of a forged Mg-7Gd-5Y-1Nd-0.5Zr alloy with different stress concentration factor(Kt),under different stress ratio(R),and along different loading direction.The smooth specimen(Kt=1),under R=0.1 and along longitude direction,shows a high fatigue strength of 162 MPa at 107 cycles.The fatigue behavior of the forged Mg-7Gd-5Y-1Nd-0.5Zr alloy exhibits a high sensitive to the notch.Moreover,change of stress ratio from 0.1 to−1 may also result in a bad fatigue property.The flux inclusions were elongated along longitude direction and/or transverse direction during the forging process of the Mg-7Gd-5Y-1Nd-0.5Zr alloy.The interface between the flux inclusion and the matrix may debond and serve as the crack initiation site during the fatigue loading process,leading to the deterioration of the fatigue property along thickness direction and a high anisotropic fatigue behavior between longitude direction and thickness direction.展开更多
基金financially supported by the National Natural Science Foundation of China(no.U21A20131)the Innovative Research Team Development Program of Ministry of Education of China(no.IRT17R83)for the support given to this research.
文摘Al5A06 sheets by large cold plastic deformation usually have high strength but low plasticity,i.e.weak strength-plasticity matching,which may lead to their poor fatigue property.In this study,annealing treat-ments are applied on cold rotary forged Al5A06 sheets to regulate strength-plasticity matching and im-prove fatigue properties.The microstructures,tensile mechanical properties and fatigue properties un-der different annealing parameters were analyzed.The abnormal grain growth mechanism of cold rotary forged Al5A06 sheets during 300℃ annealing treatment was investigated,and the fatigue failure mech-anism of Al5A06 sheets with different annealing temperatures was also investigated.The abnormal grain growth during 300℃ annealing treatment is mainly due to the asynchronous recrystallization behavior with low recrystallization driving force,which leads to the early recrystallized regions directly absorb-ing adjacent grains along134crystal direction.The cold rotary forged Al5A06 sheets after 250℃-2 h annealing treatment exhibit the best fatigue property,which is mainly because the optimum strength-plasticity matching brings about coordinate plastic deformation throughout most grains,and the effective dislocation movement between adjacent grains can delay the appearance of strain localization and ac-commodate continuous fatigue cyclic loading.
基金supported by the National Natural Science Foundation of China(No.U21A20131)the Technical Development Project of COMAC Shanghai Aircraft Manufacturing Co.,Ltd.(No.COMAC-SFGS-2023-631)the 111 Project(No.B17034),andthe In-novative Research Team Development Program of Ministry of Edu-cation of China(No.IRT17R83).
文摘Al7075 sheets are widely used in aerospace industry and their higher strength-plasticity collaborative improvement requirement is urgent.In this study,the microstructure inheriting the evolution and me-chanical properties of Al7075 sheets during multidirectional rotary forging(MRF)and T6 heat treatment are analyzed.The results show that the average grain size exhibits near-parabolic evolution with increas-ing MRF deformation amount.MRF20%+T6(20%MRF deformation amount+T6)condition possesses the largest grain size of 72.6μm,and its abnormal grain growth mechanism is that the medium deformation energy and high deformation heterogeneity in MRF20%deformed grains could cause asynchronous re-crystallization behavior during T6 heat treatment,and the grains with comparatively higher deformation energy get recrystallized firstly and devour adjacent grains along preferred011or223misorientation axis.MRF70%+T6 condition possesses the finest grain size of 14.2μm,and its fine grain inheriting mech-anism is that the uniformly high deformation energy in MRF70%deformed grains causes uniformly rapid recrystallization,and rapidly recrystallized grains effectively suppress grain boundary motion from adja-cent grains.With increasing MRF deformation amount,tensile strength and elongation values both exhibit near-antiparabolic evolution.MRF70%+T6 condition possesses the largest tensile strength(563 MPa)and elongation(17.73%),which increases by 8.27%and 80.55%compared to as-annealed+T6(MRF0%+T6)condition(tensile strength is 520 MPa and elongation is 9.82%),respectively.The strength-plasticity col-laborative improvement is mainly because the combination of effectively inherited fine grains,refined inclusion particles,and uniformly distributed fineη’particles after T6 heat treatment could promote smooth dislocation movement and coordinated slip behavior in most matrix grains,which contributes to the delay of stress localization and strength-plasticity collaborative improvement.
基金Key R&D Plan Projects in Hubei Province(Grant No.2021BID001)the Research on Multiple Regression and Fitting Technology of Simulation Data for Dynamic Umbrella Opening of Lifesaving Umbrella(Grant No.HX2021157)。
文摘In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,metallographic examination,and hardness test,the properties and causes of the cracks are discussed.The results indicate that the cracking type is intergranular brittle cracking,occurring during the forging stage.Furthermore,the recrystallization at the crack site is found to be incomplete,which is attributed to the low deformation temperature.
基金Project (2011CB605505) supported by the National Basic Research Program of ChinaProject (2008AA03A233) supported by the National High-Tech Research and Development Program of China
文摘Ti-47Al-2Nb-2Cr-0.4（W, Mo） （mole fraction, %） alloy ingot fabricated using vacuum consumable melting was containerless near-isothermally forged, and the high temperature forgeability, microstructure and tensile properties were investigated. The results show that the TiAl ingot exhibits good heat workability during containerless near-isothermally forging process, and there are not evident cracks on the surface of as-forged TiAl pancake with a total deformation degree of 60%. The microstructure of the TiAl ingot appears to be typical nearly-lamellar（NL）, comprising a great amount of lamellar colonies （α2＋γ） and a few equiaxed γ grains. After near-isothermally forging, the as-forged pancake shows primarily fine equiaxed γ grains with an average grain size of 20 μm and some broken lamellar pieces, and some bent lamellas still exist in the hard-deformation zone. Tensile tests at room temperature show that ultimate tensile strength increases from 433 MPa to 573 MPa after forging due to grain refinement effect.
基金the Jihua Laboratory Scientific Research Project,China (No.X210291TL210)the National Natural Science Foundation of China (No.51971215)the Natural Science Foundation of Liaoning Province of China (No.2019-MS-330)。
文摘The microstructural evolution and tensile properties of a forged Ti−42Al−5Mn alloy subjected to different heat treatments were studied.The results showed that,when the forged alloy was aged at 800℃ for 24 h,the interlamellar spacing(λ)andγgrain size at colony boundaries are generally coarsened.Whereas,when the alloy was first annealed at 1300℃ and then aged at 800℃ for 24 h,this coarsening of related microstructures appears less pronounced.The suggested annealing temperatures for the forged Ti−42Al−5Mn alloy are in the range of 1250−1300℃.It was found that,on the condition of the same annealing system,both the strength and ductility were improved as the aging temperature changed from 1000 to 800℃.The secondary precipitatedβo(β_(o,sec))at colony boundaries could be responsible for improving the strength,and theγphase at colony boundaries with the grain size about 6μm might be one of the main reasons for the better ductility.
基金National Natural Science Foundation of China (50275094)
文摘The dynamic recrystallization behavior of microalloyed forged steel was investigated with a compression test in the temperature range of 1 223-1 473 K and a strain rate of 0. 01-5 s^-1. Activation energy was calculated to be 305.9 kJ/mol by regression analysis. Modeling equations were developed to represent the dynamic recrystallization volume fraction and grain size. Parameters of the modeling equations were determined as a function of the Zener-Hollomon parameter. The developed modeling equation will be combined with finite element modeling to predict microstructural change during the hot forging processing.
基金Project(51301209)supported by the National Natural Science Foundation of China
文摘Transmission electron microscopy(TEM),scanning electron microscopy(SEM),hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy.The results show that the alloy exhibits splendid mechanical properties with an ultimate tensile strength of504MPa and an elongation of10.1%after aging at170°C for16h.With tensile testing temperature increasing to150°C,the strength of the alloy declines slightly to483MPa.Then,the strength drops quickly when temperature reaches over200°C.The high strength of the alloy in peak-aged condition is caused by a considerable amount ofθ'and AlMgSiCu(Q)precipitates.The relatively stable mechanical properties tested below150°C are mainly ascribed to the stability ofθ'precipitates.The growth ofθ'and Q precipitates and the generation ofθphase lead to a rapid drop of the strength when temperature is over150°C.
基金This work was funded by the National Basic Research Program of China(973 Program)through project No.2013CB632202National Natural Science Foundation of China(NSFC)through projects No.51105350 and No.51301173,respectively.
文摘This paper investigated the high cycle fatigue behavior of a forged Mg-7Gd-5Y-1Nd-0.5Zr alloy with different stress concentration factor(Kt),under different stress ratio(R),and along different loading direction.The smooth specimen(Kt=1),under R=0.1 and along longitude direction,shows a high fatigue strength of 162 MPa at 107 cycles.The fatigue behavior of the forged Mg-7Gd-5Y-1Nd-0.5Zr alloy exhibits a high sensitive to the notch.Moreover,change of stress ratio from 0.1 to−1 may also result in a bad fatigue property.The flux inclusions were elongated along longitude direction and/or transverse direction during the forging process of the Mg-7Gd-5Y-1Nd-0.5Zr alloy.The interface between the flux inclusion and the matrix may debond and serve as the crack initiation site during the fatigue loading process,leading to the deterioration of the fatigue property along thickness direction and a high anisotropic fatigue behavior between longitude direction and thickness direction.
