Heat treatable Al alloys of the 6xxx series are produced by the industry following a path that consolidates melting of raw materials, casting the melt in billets, solutionizing the billets following a suitable thermal...Heat treatable Al alloys of the 6xxx series are produced by the industry following a path that consolidates melting of raw materials, casting the melt in billets, solutionizing the billets following a suitable thermal cycle, pre-heating and extruding the material to profiles and finally aging the profiles. Although this procedure is known for pure materials from the scientific point of view, the introduction of scrap to the raw materials for melting modifies to an extent the fabrication conditions that follow casting. This fact affects the production cost. In this article we propose a research way based mainly on micro-Vickers tests that lead to an optimization of the treatment conditions for solutionizing the billets.展开更多
The present study focuses on the relationship of hardness with grain size for commercially pure titanium （CpTi） and ultra fine grained titanium （UFG-Ti） produced by equal channel angular process （ECAP） of Cp-Ti...The present study focuses on the relationship of hardness with grain size for commercially pure titanium （CpTi） and ultra fine grained titanium （UFG-Ti） produced by equal channel angular process （ECAP） of Cp-Ti）.Vickers and Knoop indentations of UFG-Ti at different loads was ～2.5 times harder than those of Cp-Ti.Xray diffraction （XRD） analysis showed peak broadening in UFG-Ti due to reduced grain size and micro-lattice strains.Scanning electron microscopy （SEM） revealed that ECAP had reduced the grain size of Cp-Ti by ～10 times.Weibull statistics showed UFG-Ti with lower dispersion in hardness values compare to Cp-Ti indicating a more uniform microstructure.展开更多
Objective The Vickers ligament is thought to hinder the growth of palmar ulnar radius by tethering the lunate to the radius,leading to Madelung deformity.The purpose of this study was to clarify the nature of the Vick...Objective The Vickers ligament is thought to hinder the growth of palmar ulnar radius by tethering the lunate to the radius,leading to Madelung deformity.The purpose of this study was to clarify the nature of the Vickers ligament and investigate its pathogenesis in Madelung deformities based on our observation of the Vickers ligament.Methods All 22 patients(33 wrists)with Madelung deformities treated surgically between 2018 and 2022 were included.The diagnosis was confirmed radiographically in all patients.The three-dimensional computed tomography(3D-CT)data of 16 patients(19 wrists)were available.Magnetic resonance imaging(MRI)data were available for 9 patients(14 wrists).Wrist arthroscopy was used in 4 patients.The Vickers ligament was resected and submitted for histopathological examination in 8 patients.Radiographic outcomes,3D-CT,MRI,arthroscopy,surgical findings,and histopathology of the Vickers ligament were evaluated.Results The 3D-CT revealed that the Vickers ligament originated in the metaphysis and formed a metaphyseal defect at the palmar ulnar radius.In the sequential MR coronal images,the Vickers ligament could be divided into 3 branches,extending to the lunate,triquetrum and ulnar styloid.Arthroscopy and surgical findings revealed that the nature of the Vickers ligament was the stretched palmar ligament of the wrist.The histopathology results revealed ligamentous tissue and fibrocartilaginous metaplasia with a structure similar to that of the triangular fibrocartilage complex(TFCC).Conclusions The Vickers ligament is not a separate aberrant ligament.The nature of the Vickers ligament is a combination of the stretched TFCC ligament(palmar radioulnar ligament,ulnotriquetral ligament and ulnolunate ligament)and radiolunate ligament.The possible pathogenesis of Madelung deformity might be focal early epiphyseal closure at the middle part of the sigmoid notch,which leads to focal growth retardation of the radius and pulls palmar ligaments proximally to form the Vickers ligament.展开更多
BTMA member Vickers Oils has marked a significant milestone in its partnership with knitting machinery leader Lonati by earning Original Equipment Manufacturer(OEM)approval for its VICKERLUBE SOCK 46needle oil.
Vickers indentation was introduced into the originally in-plane and out-of-plane poled PLZT ceramics.The Raman spectra were in-situ recorded at selected crack tips before and after the indentations,as well as after th...Vickers indentation was introduced into the originally in-plane and out-of-plane poled PLZT ceramics.The Raman spectra were in-situ recorded at selected crack tips before and after the indentations,as well as after the applications of external electric field.The results show that the changes in Raman intensities of optical modes could be sensitively related to 90° domain switching around the crack tips which are strongly dependent on the directions of original polarization and geometric locations.When the direction of electric field was perpendicular to the direction of original polarization,the 90° domain switching at crack tips of the Vickers indentation on the originally in-plane poled PLZT ceramics caused most significant change in the Raman intensity,which inhibited the crack growth.However,when the direction of electric field was parallel to the direction of original polarization,the growth of crack tips became predominantly without the 90° domain switching,which led to the crack growth.展开更多
Shielded Metal Arc Welding (SMAW) in Ductile Irons (DI) is often required by foundries for practical manufacturing reasons. The mechanical properties of the welded structures are strongly dependent on their HAZ’s wid...Shielded Metal Arc Welding (SMAW) in Ductile Irons (DI) is often required by foundries for practical manufacturing reasons. The mechanical properties of the welded structures are strongly dependent on their HAZ’s width. A model based on the behaviour of the ferritic matrix of high-Si DIs in order to make an approach in measuring their HAZ’s width is developed in this study. A series of thermal treatments on 3.35 and 3.75 wt% Si as-cast DIs and spot SMAWs is applied on these materials. The applied SMAWs are done on non-preheated and preheated samples (150℃ - 300℃). For welding we modify the amperage (100 - 140A). The micro-hardness Vickers changes in the ferrite of the as-cast samples and inside the HAZ of the welded ones can be attributed to the existence of residual stresses (RS) in the ferritic matrix and assist in estimating the HAZ’s width.展开更多
Instrumented and Vickers indentation testing and microstructure analysis were used to investigate zirconia toughened alumina （ZTA） and silicon carbide （SIC）. Several equations were studied to relate the Vickers in...Instrumented and Vickers indentation testing and microstructure analysis were used to investigate zirconia toughened alumina （ZTA） and silicon carbide （SIC）. Several equations were studied to relate the Vickers indentation hardness, Young＇s modulus and crack behavior to the fracture toughness. The frac- ture in SiC is unstable and occurs primarily by cleavage leading to a relatively low toughness of 3 MPa m1/2, which may be inappropriate for multi-hit capability. ZTA absorbs energy by plastic deformation, pore collapse, crack deviation and crack bridging and exhibits time dependent creep. With a relatively high toughness around 6.6 MPa m1/2, ZTA is promising for multi-hit capability. The higher accuracy of median equations in calculating the indentation fracture toughness and the relatively high c/a ratios above 2.5 suggest median type cracking for both SiC and ZTA. The Young＇s modulus of both ceramics was most accurately measured at lower indentation loads of about 0.5 kgf, while more accurate hardness and fracture toughness values were obtained at intermediate and at higher indentation loads beyond 5 kgf, respectively. A strong indentation size effect （ISE） was observed in both materials. The load independent hardness of SiC is 2563 HV, putting it far above the standard armor hardness requirement of 1500 HV that is barely met by ZTA.展开更多
Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The hom...Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The homogeneity of microstructure of cold closed-die forged gears can highly affect their service performance. The homogeneity of microstructure and Vickers hardness in cold closed-die forged gear of 20 Cr Mn Ti alloy is comprehensively studied by using optical microscopy and Vickers hardness tester. The results show that the distribution homogeneity of the aspect ratio of grain and Vickers hardness is the same. In the circumferential direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous and they gradually decrease from the surface to the center of the tooth. In the radial direction, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous on the surface of the gear tooth; while it is relatively homogeneous in the center of the gear tooth. In the axial direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is relatively homogeneous from the small-end to the large-end of the gear tooth.展开更多
The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated....The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated. Lamellar structure consisted of Mo_5Si_3 (D8m) phaseand MoSi_2 (C11_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2 hypoeutectic alloy, thelamellar structure was found only after annealing and developed well with fine spacing on the orderof hundred nanometers after annealing at 1200℃ for 48 h. But when the annealing time was up to 96h, the well-developed lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, thelamellar structure was found both before and after annealing. However the volume fraction andspacing of the lamellar structure did not change significantly before and after annealing. Theeffects of the formation, development and destruction of lamellar structure on Vickers hardness ofalloys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48 h,the Vickers hardness was improved about 19% compared with that without annealing and formation oflamellar structure. The highest Vickers hardness of Mo5Si3-MoSi_2 hypereutectic was increasing about18% when annealing at 1200℃ for 48 h.展开更多
The application of friction stir welding(FSW) is growing owing to the omission of difficulties in traditional welding processes. In the current investigation, artificial neural network(ANN) technique was employed to p...The application of friction stir welding(FSW) is growing owing to the omission of difficulties in traditional welding processes. In the current investigation, artificial neural network(ANN) technique was employed to predict the microhardness of AA6061 friction stir welded plates. Specimens were welded employing triangular and tapered cylindrical pins. The effects of thread and conical shoulder of each pin profile on the microhardness of welded zone were studied using tow ANNs through the different distances from weld centerline. It is observed that using conical shoulder tools enhances the quality of welded area. Besides, in both pin profiles threaded pins and conical shoulders increase yield strength and ultimate tensile strength. Mean absolute percentage error(MAPE) for train and test data sets did not exceed 5.4% and 7.48%, respectively. Considering the accurate results and acceptable errors in the models' responses, the ANN method can be used to economize material and time.展开更多
In this work,the Sn-58Bi(weight percent) eutectic alloy was directionally solidified at a constant temperature gradient(G = 12 K.mm-1) with different growth rates using a Bridgman type directional solidification furna...In this work,the Sn-58Bi(weight percent) eutectic alloy was directionally solidified at a constant temperature gradient(G = 12 K.mm-1) with different growth rates using a Bridgman type directional solidification furnace.A lamellar microstructure was observed in the Sn-58Bi samples.The lamellar spacing and micro-hardness of longitudinal and transversal sections were measured.The values of lamellar spacing of both longitudinal and transversal sections decrease with an increase in growth rate.The microhardness increases with an increase in the growth rate and decreases with an increase in the lamellar spacing.The dependence of lamellar spacing on growth rate,and micro-hardness on both growth rate and lamellar spacing were obtained by linear regression analysis.The relationships between the lamellar spacing and growth rate,microhardness and growth rate,and micro-hardness and lamellar spacing for transversal and longitudinal sections of Sn-58Bi eutectic alloy were given.The fitted exponent values obtained in this work were compared with the previous similar experimental results and a good agreement was obtained.展开更多
The Vickers hardness test has been widely used for neutron-irradiated materials and nanoindentation for ion-irradiated materials.Comparing the Vickers hardness and nanohardness of the same materials quantitatively and...The Vickers hardness test has been widely used for neutron-irradiated materials and nanoindentation for ion-irradiated materials.Comparing the Vickers hardness and nanohardness of the same materials quantitatively and establishing a correlation between them is meaningful.In this study,five representative materials—pure titanium(Ti),nickel(Ni),tungsten(W),304 coarse-grained stainless steel(CG-SS)and 304 nanocrystalline austenitic stainless steel(NG-SS)—are investigated for comparison.The results show that the relationship between Vickers hardness and nanohardness does not conform to a mathematical geometric relationship because of sink-in and pile-up effects confirmed by finite element analysis(FEA)and the results of optical microscopy.Finally,one new method was developed by excluding the effects of sink-in and pile-up in materials.With this improved correction in the projected area of the Vickers hardness and nanohardness,the two kinds of hardness become identical.展开更多
Numerical simulation and experimental study of the Vickers indentation testing of the Al2O3 ceramic coated by diamond-like carbon(DLC) layer were conducted.The numerical analysis was implemented by a two-dimensional f...Numerical simulation and experimental study of the Vickers indentation testing of the Al2O3 ceramic coated by diamond-like carbon(DLC) layer were conducted.The numerical analysis was implemented by a two-dimensional finite element(FE) axis symmetry model.FE analysis results gave insight into the fracture mechanism of DLC films coated on brittle ceramic(Al2O3) substrates.The maximum principal stress field was used to locate the most expected area for crack formation and propagation during the Vickers indentation testing.The results show that the median crack initiates in the interface under indenter,before ring crack occurs as the indenter presses down.Finally,the plastic deformation appears when the indenter penetrates into the substrate.The thicker DLC coating increases the Vickers hardness and fracture toughness.展开更多
For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and...For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and low density besides its ability to retain strength and stiffness at elevated temperatures. However NiAl intermetallic is too hard, brittle and exhibits very low ductility at room temperature being the reason because this material is not yet available for structural applications. In order to increase the ductility of the NiAl intermetallic compound, the addition of a third alloying element has been proved, nevertheless it is important to determine if such additions decrease or increase the hardness and the corrosion resistance of the alloy. So, the present investigation reports the corrosion performance of the NiAl intermetallic compound modified with Cu, emphasizing the EIS analysis and the relation between physical parameters and the modelling equations used in the Equivalent Electric Circuit. It was found that the addition of Cu promotes the formation of the γ’-Ni<sub>3</sub>Al phase in Cu contents greater than 15 at. %, in addition to a decrease in micro hardness and an increment in the I<sub>corr</sub> values. In this way, the electrochemical characterization evidenced a high corrosion resistance of these intermetallic alloys.展开更多
文摘Heat treatable Al alloys of the 6xxx series are produced by the industry following a path that consolidates melting of raw materials, casting the melt in billets, solutionizing the billets following a suitable thermal cycle, pre-heating and extruding the material to profiles and finally aging the profiles. Although this procedure is known for pure materials from the scientific point of view, the introduction of scrap to the raw materials for melting modifies to an extent the fabrication conditions that follow casting. This fact affects the production cost. In this article we propose a research way based mainly on micro-Vickers tests that lead to an optimization of the treatment conditions for solutionizing the billets.
文摘The present study focuses on the relationship of hardness with grain size for commercially pure titanium （CpTi） and ultra fine grained titanium （UFG-Ti） produced by equal channel angular process （ECAP） of Cp-Ti）.Vickers and Knoop indentations of UFG-Ti at different loads was ～2.5 times harder than those of Cp-Ti.Xray diffraction （XRD） analysis showed peak broadening in UFG-Ti due to reduced grain size and micro-lattice strains.Scanning electron microscopy （SEM） revealed that ECAP had reduced the grain size of Cp-Ti by ～10 times.Weibull statistics showed UFG-Ti with lower dispersion in hardness values compare to Cp-Ti indicating a more uniform microstructure.
基金supported by the Natural Science Foundation of Beijing Municipality(No.7222087)Beijing JST Research Funding(No.ZR-202217).
文摘Objective The Vickers ligament is thought to hinder the growth of palmar ulnar radius by tethering the lunate to the radius,leading to Madelung deformity.The purpose of this study was to clarify the nature of the Vickers ligament and investigate its pathogenesis in Madelung deformities based on our observation of the Vickers ligament.Methods All 22 patients(33 wrists)with Madelung deformities treated surgically between 2018 and 2022 were included.The diagnosis was confirmed radiographically in all patients.The three-dimensional computed tomography(3D-CT)data of 16 patients(19 wrists)were available.Magnetic resonance imaging(MRI)data were available for 9 patients(14 wrists).Wrist arthroscopy was used in 4 patients.The Vickers ligament was resected and submitted for histopathological examination in 8 patients.Radiographic outcomes,3D-CT,MRI,arthroscopy,surgical findings,and histopathology of the Vickers ligament were evaluated.Results The 3D-CT revealed that the Vickers ligament originated in the metaphysis and formed a metaphyseal defect at the palmar ulnar radius.In the sequential MR coronal images,the Vickers ligament could be divided into 3 branches,extending to the lunate,triquetrum and ulnar styloid.Arthroscopy and surgical findings revealed that the nature of the Vickers ligament was the stretched palmar ligament of the wrist.The histopathology results revealed ligamentous tissue and fibrocartilaginous metaplasia with a structure similar to that of the triangular fibrocartilage complex(TFCC).Conclusions The Vickers ligament is not a separate aberrant ligament.The nature of the Vickers ligament is a combination of the stretched TFCC ligament(palmar radioulnar ligament,ulnotriquetral ligament and ulnolunate ligament)and radiolunate ligament.The possible pathogenesis of Madelung deformity might be focal early epiphyseal closure at the middle part of the sigmoid notch,which leads to focal growth retardation of the radius and pulls palmar ligaments proximally to form the Vickers ligament.
文摘BTMA member Vickers Oils has marked a significant milestone in its partnership with knitting machinery leader Lonati by earning Original Equipment Manufacturer(OEM)approval for its VICKERLUBE SOCK 46needle oil.
基金Project(2006L2003)supported by the Fujian Key Laboratory of Advanced Materials,ChinaProject(10802070)supported by the National Natural Science Foundation of China
文摘Vickers indentation was introduced into the originally in-plane and out-of-plane poled PLZT ceramics.The Raman spectra were in-situ recorded at selected crack tips before and after the indentations,as well as after the applications of external electric field.The results show that the changes in Raman intensities of optical modes could be sensitively related to 90° domain switching around the crack tips which are strongly dependent on the directions of original polarization and geometric locations.When the direction of electric field was perpendicular to the direction of original polarization,the 90° domain switching at crack tips of the Vickers indentation on the originally in-plane poled PLZT ceramics caused most significant change in the Raman intensity,which inhibited the crack growth.However,when the direction of electric field was parallel to the direction of original polarization,the growth of crack tips became predominantly without the 90° domain switching,which led to the crack growth.
文摘Shielded Metal Arc Welding (SMAW) in Ductile Irons (DI) is often required by foundries for practical manufacturing reasons. The mechanical properties of the welded structures are strongly dependent on their HAZ’s width. A model based on the behaviour of the ferritic matrix of high-Si DIs in order to make an approach in measuring their HAZ’s width is developed in this study. A series of thermal treatments on 3.35 and 3.75 wt% Si as-cast DIs and spot SMAWs is applied on these materials. The applied SMAWs are done on non-preheated and preheated samples (150℃ - 300℃). For welding we modify the amperage (100 - 140A). The micro-hardness Vickers changes in the ferrite of the as-cast samples and inside the HAZ of the welded ones can be attributed to the existence of residual stresses (RS) in the ferritic matrix and assist in estimating the HAZ’s width.
基金partially supported by the DRDC-Valcartier,via DND funded project A1-000968
文摘Instrumented and Vickers indentation testing and microstructure analysis were used to investigate zirconia toughened alumina （ZTA） and silicon carbide （SIC）. Several equations were studied to relate the Vickers indentation hardness, Young＇s modulus and crack behavior to the fracture toughness. The frac- ture in SiC is unstable and occurs primarily by cleavage leading to a relatively low toughness of 3 MPa m1/2, which may be inappropriate for multi-hit capability. ZTA absorbs energy by plastic deformation, pore collapse, crack deviation and crack bridging and exhibits time dependent creep. With a relatively high toughness around 6.6 MPa m1/2, ZTA is promising for multi-hit capability. The higher accuracy of median equations in calculating the indentation fracture toughness and the relatively high c/a ratios above 2.5 suggest median type cracking for both SiC and ZTA. The Young＇s modulus of both ceramics was most accurately measured at lower indentation loads of about 0.5 kgf, while more accurate hardness and fracture toughness values were obtained at intermediate and at higher indentation loads beyond 5 kgf, respectively. A strong indentation size effect （ISE） was observed in both materials. The load independent hardness of SiC is 2563 HV, putting it far above the standard armor hardness requirement of 1500 HV that is barely met by ZTA.
基金Project(51105287)supported by the National Natural Science Foundation of ChinaProject(2013M531750)supported by China Postdoctoral Science Foundation
文摘Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The homogeneity of microstructure of cold closed-die forged gears can highly affect their service performance. The homogeneity of microstructure and Vickers hardness in cold closed-die forged gear of 20 Cr Mn Ti alloy is comprehensively studied by using optical microscopy and Vickers hardness tester. The results show that the distribution homogeneity of the aspect ratio of grain and Vickers hardness is the same. In the circumferential direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous and they gradually decrease from the surface to the center of the tooth. In the radial direction, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous on the surface of the gear tooth; while it is relatively homogeneous in the center of the gear tooth. In the axial direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is relatively homogeneous from the small-end to the large-end of the gear tooth.
文摘The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated. Lamellar structure consisted of Mo_5Si_3 (D8m) phaseand MoSi_2 (C11_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2 hypoeutectic alloy, thelamellar structure was found only after annealing and developed well with fine spacing on the orderof hundred nanometers after annealing at 1200℃ for 48 h. But when the annealing time was up to 96h, the well-developed lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, thelamellar structure was found both before and after annealing. However the volume fraction andspacing of the lamellar structure did not change significantly before and after annealing. Theeffects of the formation, development and destruction of lamellar structure on Vickers hardness ofalloys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48 h,the Vickers hardness was improved about 19% compared with that without annealing and formation oflamellar structure. The highest Vickers hardness of Mo5Si3-MoSi_2 hypereutectic was increasing about18% when annealing at 1200℃ for 48 h.
文摘The application of friction stir welding(FSW) is growing owing to the omission of difficulties in traditional welding processes. In the current investigation, artificial neural network(ANN) technique was employed to predict the microhardness of AA6061 friction stir welded plates. Specimens were welded employing triangular and tapered cylindrical pins. The effects of thread and conical shoulder of each pin profile on the microhardness of welded zone were studied using tow ANNs through the different distances from weld centerline. It is observed that using conical shoulder tools enhances the quality of welded area. Besides, in both pin profiles threaded pins and conical shoulders increase yield strength and ultimate tensile strength. Mean absolute percentage error(MAPE) for train and test data sets did not exceed 5.4% and 7.48%, respectively. Considering the accurate results and acceptable errors in the models' responses, the ANN method can be used to economize material and time.
基金financially supported by the China Postdoctoral Science Foundation(No.20110491492)Nature Science Foundation of Jiangxi Province(Nos.20114BAB216017,20114BAB206021)the Science and Technology Project of Jiangxi Department of Education(No.GJJ12035)
文摘In this work,the Sn-58Bi(weight percent) eutectic alloy was directionally solidified at a constant temperature gradient(G = 12 K.mm-1) with different growth rates using a Bridgman type directional solidification furnace.A lamellar microstructure was observed in the Sn-58Bi samples.The lamellar spacing and micro-hardness of longitudinal and transversal sections were measured.The values of lamellar spacing of both longitudinal and transversal sections decrease with an increase in growth rate.The microhardness increases with an increase in the growth rate and decreases with an increase in the lamellar spacing.The dependence of lamellar spacing on growth rate,and micro-hardness on both growth rate and lamellar spacing were obtained by linear regression analysis.The relationships between the lamellar spacing and growth rate,microhardness and growth rate,and micro-hardness and lamellar spacing for transversal and longitudinal sections of Sn-58Bi eutectic alloy were given.The fitted exponent values obtained in this work were compared with the previous similar experimental results and a good agreement was obtained.
基金financially supported by the National Magnetic Confinement Fusion Energy Research Project of China(No.2015GB113000)National Natural Science Foundation of China(Nos.11675005,11935004)+1 种基金China Postdoctoral Science Foundation(No.2018M641093)the National Defense Nuclear Material Technology Innovation Center。
文摘The Vickers hardness test has been widely used for neutron-irradiated materials and nanoindentation for ion-irradiated materials.Comparing the Vickers hardness and nanohardness of the same materials quantitatively and establishing a correlation between them is meaningful.In this study,five representative materials—pure titanium(Ti),nickel(Ni),tungsten(W),304 coarse-grained stainless steel(CG-SS)and 304 nanocrystalline austenitic stainless steel(NG-SS)—are investigated for comparison.The results show that the relationship between Vickers hardness and nanohardness does not conform to a mathematical geometric relationship because of sink-in and pile-up effects confirmed by finite element analysis(FEA)and the results of optical microscopy.Finally,one new method was developed by excluding the effects of sink-in and pile-up in materials.With this improved correction in the projected area of the Vickers hardness and nanohardness,the two kinds of hardness become identical.
文摘Numerical simulation and experimental study of the Vickers indentation testing of the Al2O3 ceramic coated by diamond-like carbon(DLC) layer were conducted.The numerical analysis was implemented by a two-dimensional finite element(FE) axis symmetry model.FE analysis results gave insight into the fracture mechanism of DLC films coated on brittle ceramic(Al2O3) substrates.The maximum principal stress field was used to locate the most expected area for crack formation and propagation during the Vickers indentation testing.The results show that the median crack initiates in the interface under indenter,before ring crack occurs as the indenter presses down.Finally,the plastic deformation appears when the indenter penetrates into the substrate.The thicker DLC coating increases the Vickers hardness and fracture toughness.
文摘For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and low density besides its ability to retain strength and stiffness at elevated temperatures. However NiAl intermetallic is too hard, brittle and exhibits very low ductility at room temperature being the reason because this material is not yet available for structural applications. In order to increase the ductility of the NiAl intermetallic compound, the addition of a third alloying element has been proved, nevertheless it is important to determine if such additions decrease or increase the hardness and the corrosion resistance of the alloy. So, the present investigation reports the corrosion performance of the NiAl intermetallic compound modified with Cu, emphasizing the EIS analysis and the relation between physical parameters and the modelling equations used in the Equivalent Electric Circuit. It was found that the addition of Cu promotes the formation of the γ’-Ni<sub>3</sub>Al phase in Cu contents greater than 15 at. %, in addition to a decrease in micro hardness and an increment in the I<sub>corr</sub> values. In this way, the electrochemical characterization evidenced a high corrosion resistance of these intermetallic alloys.
