The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature r...The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature range from 900 to 940℃, pressure over 100 MPa and holding time of 3 h, were obtained. Tensile properties after different heat treatments show that both the geometry of samples and cooling rate have a significant influence on mechanical properties. Finite element method was used to predict the temperature field distribution during HIPped sample cooling, and the experimental results are in agreement with simulation prediction. The interaction of HIPping parameters was analyzed based on the response surface methodology（RSM） in this study.展开更多
Diffusion bonding between aluminum and copper was performed by vacuum hot pressing at temperatures between 623 and 923 K through two thermal processes： hot compression under the deformation rate of 0.2 mrrdmin for 10...Diffusion bonding between aluminum and copper was performed by vacuum hot pressing at temperatures between 623 and 923 K through two thermal processes： hot compression under the deformation rate of 0.2 mrrdmin for 10 rain at pre-set temperatures, and additional pressing at 0.2 mm/min for 20 rain during furnace cooling. After analyzing interface, the feasible diffusion bonding temperature was suggested as 823 K. The three major intermetallic layers generated during diffusion bonding process were identified as AIECu, AlCu＋AlaCu4 and Al4Cu9. Furthermore, local hardness values ofAlECU, AlCu＋AlaCu4 and Al4Cu9 layers average at （4.97±0.05）, （6.33±0.00） and （6.06±0.18） GPa, respectively.展开更多
The aim of this work was to study the influence of the processing route on the microstructural constituents,hardness andtribological(wear and friction)behavior of Ti6Al4V biomedical alloy.In this sense,three different...The aim of this work was to study the influence of the processing route on the microstructural constituents,hardness andtribological(wear and friction)behavior of Ti6Al4V biomedical alloy.In this sense,three different processing routes were studied:conventional casting,hot pressing and selective laser melting.A comprehensive metallurgical,mechanical and tribologicalcharacterization was performed by X-ray diffraction analysis,Vickers hardness tests and reciprocating ball-on-plate wear tests ofTi6Al4V/Al2O3sliding pairs.The results showed a great influence of the processing route on the microstructural constituents andconsequent differences on hardness and wear performance.The highest hardness and wear resistance were obtained for Ti6Al4Valloy produced by selective laser melting,due to a markedly different cooling rate that leads to significantly different microstructurewhen compared to hot pressing and casting.This study assesses and confirms that selective laser melting is potential to producecustomized Ti6Al4V implants with improved wear performance.展开更多
Pre-alloyed powder of Ti-22Al-24Nb-0.5Mo（atomic fraction,%） was prepared by gas atomization.Powder metallurgy（PM） Ti 2AlNb alloys were prepared by a hot isostatic pressing（HIPing） route.The influence of experime...Pre-alloyed powder of Ti-22Al-24Nb-0.5Mo（atomic fraction,%） was prepared by gas atomization.Powder metallurgy（PM） Ti 2AlNb alloys were prepared by a hot isostatic pressing（HIPing） route.The influence of experimental variables including HIPing temperatures,solution and aging temperatures on microstructure and properties of PM Ti 2AlNb alloys was studied.The results showed that HIPing temperature affected the porosity distribution and mechanical properties of PM Ti 2AlNb alloys.The microstructure and mechanical properties of the PM Ti 2AlNb alloys changed obviously after various post heat treatments,and a good combination of tensile strength,ductility and rupture lifetime was obtained through an optimized heat treatment in the present work.展开更多
In this study,the multi-pass equal channel angular pressing(ECAP)was employed on a high-calcium-content Mg-Al-Ca-Mn alloy to tailor its microstructure and mechanical properties.The obtained results showed that the net...In this study,the multi-pass equal channel angular pressing(ECAP)was employed on a high-calcium-content Mg-Al-Ca-Mn alloy to tailor its microstructure and mechanical properties.The obtained results showed that the network-shaped Mg2Ca and(Mg,Al)2Ca eutectic compounds in as-cast alloy were gradually crushed into ultra-fine particles after ECAP,which exhibited a bimodal particle size distribution and most aggregated at original grain boundaries.Dynamic recrystallization(DRX)of α-Mg occurred during hot deformation via a particle stimulated mechanism,and the almost complete DRX with an average grain size around 1.5μm was obtained after 12p-ECAP.Moreover,abundant nano-sized acicular and spherical precipitates were dynamically precipitated withinα-Mg grains during ECAP.Tensile test results indicated that the maximum strength and ductility were acquired for 12p-ECAP alloy with ultimate tensile strength of 372 MPa and fracture elongation of 8%.The enhanced strength of the alloy could be ascribed to fine DRX grains,ultra-fine Ca-containing particles and dynamically precipitated nano-precipitates,while the improved ductility was mainly due to the refined and homogeneous microstructure,and weak texture with high average Schmid factors.展开更多
Objective： To explore the therapeutical effect of ear-acupoint pressing combined with Ear Apex （HX6,7） bloodletting on haemorheology in chloasma patients with Gan （Liver） depression pattern. Methods： A total of ...Objective： To explore the therapeutical effect of ear-acupoint pressing combined with Ear Apex （HX6,7） bloodletting on haemorheology in chloasma patients with Gan （Liver） depression pattern. Methods： A total of 180 chloasma patients were randomly assigned to three groups, 60 cases in each. Patients in the ear- acupuncture （EA） group were treated with ear-acupoint pressing combined with Ear Apex（HX6,7） bloodletting; vitamins C and E were put into practice in the Western medicine （WM） group together with 0.025% tretinoin cream for local external application; patients in the placebo group were treated with urea-cream by external use, while 30 healthy volunteers were in the control group. After a treatment course of 2 months, the changes of haemorheology, injury skin area, colour score and symptom score before and after the treatment were observed. Results： There was no significant difference on whole blood reduced viscosity （high shear, medium shear, and low shear）, erythrocyte aggregation index, hematocrit, plasma viscosity among the four groups （F=2.65, P〉0.05）. Compared with those before treatment, the whole blood viscosity （high shear） and whole blood reduced viscosity （high shear） after treatment in the EA group, the WM group and the placebo group were with no statistical significance （P〉0.05）. The injury skin area and colour score after treatment were significantly lower than those before treatment in the EA group and the WM group （P〈0.05）, while there was no significant difference in placebo group （P〉0.05）. Clinical symptoms of the EA group were obviously improved after the 2-month treatment, which was significantly different compared with those before treatment （P〈0.05）, there was significant difference compared with those of WM group and placebo group （P〈0.05）. Conclusion： There was no significant difference on haemorheology index between healthy people and chloasma patients without angionosis, cerebrovascular disease, hematopathy, 展开更多
Ultra-fine grained （UFG） cylindrical tubes were produced via recently developed tubular channel angular pressing （TCAP） process through different passes from as-cast AZ91 magnesium alloy. The microstructure and me...Ultra-fine grained （UFG） cylindrical tubes were produced via recently developed tubular channel angular pressing （TCAP） process through different passes from as-cast AZ91 magnesium alloy. The microstructure and mechanical properties of processed tube through one to four passes of TCAP process at 200℃ were investigated. Microhardness of the processed tube was increased to 98.5 HV after one pass from an initial value of 67 Hr. An increase in the number of passes from one to higher number of passes has no more effect on the microhardness. Yield and ultimate strengths were increased by 4.3 and 1.4 times compared to those in as-cast condition. Notable increase in the strength was achieved after one pass of TCAP while higher number of passes has no more effect. Microstructural investigation shows notable decrease in the grain size to around 500 nm from the primary value of - 150 μm. Dissolution and distribution of hard MglTAI12 phase in the grain boundaries of dynamically recrystallized UFG AZ91 with a mean grain size of - 500 nm was an interesting issue of TCAP processing at 200 ℃ compared to other severe plastic deformation processes.展开更多
文摘The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature range from 900 to 940℃, pressure over 100 MPa and holding time of 3 h, were obtained. Tensile properties after different heat treatments show that both the geometry of samples and cooling rate have a significant influence on mechanical properties. Finite element method was used to predict the temperature field distribution during HIPped sample cooling, and the experimental results are in agreement with simulation prediction. The interaction of HIPping parameters was analyzed based on the response surface methodology（RSM） in this study.
基金Project (10037273) supported by the Ministry of Knowledge Economy, Korea
文摘Diffusion bonding between aluminum and copper was performed by vacuum hot pressing at temperatures between 623 and 923 K through two thermal processes： hot compression under the deformation rate of 0.2 mrrdmin for 10 rain at pre-set temperatures, and additional pressing at 0.2 mm/min for 20 rain during furnace cooling. After analyzing interface, the feasible diffusion bonding temperature was suggested as 823 K. The three major intermetallic layers generated during diffusion bonding process were identified as AIECu, AlCu＋AlaCu4 and Al4Cu9. Furthermore, local hardness values ofAlECU, AlCu＋AlaCu4 and Al4Cu9 layers average at （4.97±0.05）, （6.33±0.00） and （6.06±0.18） GPa, respectively.
基金supported by FTC through the projects PTDC/EMS-TEC/5422/2014 and EXCL/EMS-TEC/ 0460/2012the grant SFRH/BPD/112111/2015+1 种基金supported by FCT with the reference project UID/EEA/04436/2013by FEDER funds through the COMPETE 2020-Programa Operacional Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145FEDER-006941.
文摘The aim of this work was to study the influence of the processing route on the microstructural constituents,hardness andtribological(wear and friction)behavior of Ti6Al4V biomedical alloy.In this sense,three different processing routes were studied:conventional casting,hot pressing and selective laser melting.A comprehensive metallurgical,mechanical and tribologicalcharacterization was performed by X-ray diffraction analysis,Vickers hardness tests and reciprocating ball-on-plate wear tests ofTi6Al4V/Al2O3sliding pairs.The results showed a great influence of the processing route on the microstructural constituents andconsequent differences on hardness and wear performance.The highest hardness and wear resistance were obtained for Ti6Al4Valloy produced by selective laser melting,due to a markedly different cooling rate that leads to significantly different microstructurewhen compared to hot pressing and casting.This study assesses and confirms that selective laser melting is potential to producecustomized Ti6Al4V implants with improved wear performance.
文摘Pre-alloyed powder of Ti-22Al-24Nb-0.5Mo（atomic fraction,%） was prepared by gas atomization.Powder metallurgy（PM） Ti 2AlNb alloys were prepared by a hot isostatic pressing（HIPing） route.The influence of experimental variables including HIPing temperatures,solution and aging temperatures on microstructure and properties of PM Ti 2AlNb alloys was studied.The results showed that HIPing temperature affected the porosity distribution and mechanical properties of PM Ti 2AlNb alloys.The microstructure and mechanical properties of the PM Ti 2AlNb alloys changed obviously after various post heat treatments,and a good combination of tensile strength,ductility and rupture lifetime was obtained through an optimized heat treatment in the present work.
基金This work was supported by the Natural Science Foun-dation of China(51901068)the Natural Science Foundation of Jiangsu Province of China(BK20160869)+1 种基金the Fundamental Research Funds for the Central Universities(2018B16614)the Nantong Science and Technology Project.
文摘In this study,the multi-pass equal channel angular pressing(ECAP)was employed on a high-calcium-content Mg-Al-Ca-Mn alloy to tailor its microstructure and mechanical properties.The obtained results showed that the network-shaped Mg2Ca and(Mg,Al)2Ca eutectic compounds in as-cast alloy were gradually crushed into ultra-fine particles after ECAP,which exhibited a bimodal particle size distribution and most aggregated at original grain boundaries.Dynamic recrystallization(DRX)of α-Mg occurred during hot deformation via a particle stimulated mechanism,and the almost complete DRX with an average grain size around 1.5μm was obtained after 12p-ECAP.Moreover,abundant nano-sized acicular and spherical precipitates were dynamically precipitated withinα-Mg grains during ECAP.Tensile test results indicated that the maximum strength and ductility were acquired for 12p-ECAP alloy with ultimate tensile strength of 372 MPa and fracture elongation of 8%.The enhanced strength of the alloy could be ascribed to fine DRX grains,ultra-fine Ca-containing particles and dynamically precipitated nano-precipitates,while the improved ductility was mainly due to the refined and homogeneous microstructure,and weak texture with high average Schmid factors.
基金Supported by Zhejiang Province Science and Technology Project of Traditional Chinese Medicine(No.2010B501678)
文摘Objective： To explore the therapeutical effect of ear-acupoint pressing combined with Ear Apex （HX6,7） bloodletting on haemorheology in chloasma patients with Gan （Liver） depression pattern. Methods： A total of 180 chloasma patients were randomly assigned to three groups, 60 cases in each. Patients in the ear- acupuncture （EA） group were treated with ear-acupoint pressing combined with Ear Apex（HX6,7） bloodletting; vitamins C and E were put into practice in the Western medicine （WM） group together with 0.025% tretinoin cream for local external application; patients in the placebo group were treated with urea-cream by external use, while 30 healthy volunteers were in the control group. After a treatment course of 2 months, the changes of haemorheology, injury skin area, colour score and symptom score before and after the treatment were observed. Results： There was no significant difference on whole blood reduced viscosity （high shear, medium shear, and low shear）, erythrocyte aggregation index, hematocrit, plasma viscosity among the four groups （F=2.65, P〉0.05）. Compared with those before treatment, the whole blood viscosity （high shear） and whole blood reduced viscosity （high shear） after treatment in the EA group, the WM group and the placebo group were with no statistical significance （P〉0.05）. The injury skin area and colour score after treatment were significantly lower than those before treatment in the EA group and the WM group （P〈0.05）, while there was no significant difference in placebo group （P〉0.05）. Clinical symptoms of the EA group were obviously improved after the 2-month treatment, which was significantly different compared with those before treatment （P〈0.05）, there was significant difference compared with those of WM group and placebo group （P〈0.05）. Conclusion： There was no significant difference on haemorheology index between healthy people and chloasma patients without angionosis, cerebrovascular disease, hematopathy,
基金financially supported by Iran National Science Foundation(INSF)
文摘Ultra-fine grained （UFG） cylindrical tubes were produced via recently developed tubular channel angular pressing （TCAP） process through different passes from as-cast AZ91 magnesium alloy. The microstructure and mechanical properties of processed tube through one to four passes of TCAP process at 200℃ were investigated. Microhardness of the processed tube was increased to 98.5 HV after one pass from an initial value of 67 Hr. An increase in the number of passes from one to higher number of passes has no more effect on the microhardness. Yield and ultimate strengths were increased by 4.3 and 1.4 times compared to those in as-cast condition. Notable increase in the strength was achieved after one pass of TCAP while higher number of passes has no more effect. Microstructural investigation shows notable decrease in the grain size to around 500 nm from the primary value of - 150 μm. Dissolution and distribution of hard MglTAI12 phase in the grain boundaries of dynamically recrystallized UFG AZ91 with a mean grain size of - 500 nm was an interesting issue of TCAP processing at 200 ℃ compared to other severe plastic deformation processes.
