For the purpose of investigating the dynamic deformational behavior and failure mechanisms of magnesium under high strain rates,the Split Hopkinson Pressure Bar(SHPB)was used for investigating dynamic mechanical prope...For the purpose of investigating the dynamic deformational behavior and failure mechanisms of magnesium under high strain rates,the Split Hopkinson Pressure Bar(SHPB)was used for investigating dynamic mechanical properties of extruded Mg-Gd-Y Magnesium alloy at ambient temperature(300 K),200℃(473 K)and 300℃(573 K)temperature.The samples after compression were analyzed by scanning electron microscope(SEM)and metallographic microscope.Dynamic mechanical properties,crack performance and plastic deformation mechanism of extruded Mg-Gd-Y Magnesium alloy along the extrusion direction(ED)were discussed.The results show that,extruded Mg-Gd-Y Magnesium alloy has the largest dynamic compressive strength which is 535 MPa at ambient temperature(300 K)and strain rate of 2826 s^(−1).When temperature increases,dynamic compressive strength decreases,while ductility increases.The dynamic compression fracture mechanism of extruded Mg-Gd-Y Magnesium alloy is multi-crack propagation and intergranular quasi-cleavage fracture at both ambient temperature and high temperature.The dynamic compressive deformation mechanism of extruded Mg-Gd-Y Magnesium alloy is a combination of twinning,slipping and dynamic recrystallization at both ambient temperature and high temperature.展开更多
A combination of hard(SiCP)and soft(fly ash)particulate reinforcements could be a strategy to enhance combination of multiple properties of Magnesium and its alloys which otherwise suffer from low stiffness,low wear r...A combination of hard(SiCP)and soft(fly ash)particulate reinforcements could be a strategy to enhance combination of multiple properties of Magnesium and its alloys which otherwise suffer from low stiffness,low wear resistance,and many other critical properties.However,at present a comprehensive and robust map correlating different properties in particle-reinforced composites is much lacking.In this work,an industrial grade AZ91 magnesium alloy reinforced with hard SiC and soft fly ash particles(with 3 vol.%each),has been prepared using stir casting followed by hot extrusion at 325℃with a ratio of 21.5.Microstructure of the hybrid composite was characterized using optical and scanning electron microscopes.The composite exhibited a reduction in average grain size from 13.6 to 7.1μm,concomitantly an increase in Vickers hardness from 73 to 111 HV.The tension-compression yield asymmetry ratios of the unreinforced alloy and hybrid composite were 1.165 and 0.976,respectively indicating higher yield strength for the composite under compressive load.The composite exhibited 76%improvement in damping capacity under time sweep mode,and 28%improvement at 423 K under temperature sweep mode.The tribological characteristics of the composite under dry sliding conditions at sliding speeds and loads in the range of 0.5 to 1.5 m s^(-1)and 10 to 30 N,respectively showed higher wear resistance than the unreinforced alloy.The composite showed 23%improvement in sliding wear resistance at a load of 20 N and a speed of 1 m s^(-1).Finally,efforts have been made to understand the influence of one property on the other by developing statistical property correlation maps from the properties obtained in this study and from the literature.These maps are expected to help in the design of hybrid Metal Matrix Composites for a variety of targeted applications in different sectors.展开更多
To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex conf...To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex configuration features and abrupt cross-sectional transitions was fabricated by liquid-solid extrusion following vacuum pressure infiltration process(LSEVI).Near-net forming schemes of both the special-shaped fiber preform and composite part were proposed.The effect of process parameters on the forming quality of the composite part was discussed.Meanwhile,the microstructures and compressive properties in different regions of the part were analyzed.The results show that the forward forming scheme provides the special-shaped fiber preform with no surface defects.For the C_(sf)/AZ91D part,its internal microstructures show that the infiltration of liquid magnesium is sufficient and uniform.The compressive strength of the composite part can reach up to 487 MPa,corresponding to~40%increase compared to 335 MPa of the AZ91D alloy.The average compressive strain of composites is less than 10%,which is about 50%of that of the AZ91D alloy.When the fiber orientation is parallel to the shear direction on the shear plane,the load-bearing capacity of the fiber is much higher than that of the fiber perpendicular to the shear direction.This work not only provides a convenient approach to fabricate special-shaped preform with high fiber volume fraction,but also gives a demonstration for the near-net forming of C_(sf)/Mg parts with excellent material isotropy and compressive properties.展开更多
Metamaterials are defined as artificially designed micro-architectures with unusual physical properties,including optical,electromagnetic,mechanical,and thermal characteristics.This study investigates the compressive ...Metamaterials are defined as artificially designed micro-architectures with unusual physical properties,including optical,electromagnetic,mechanical,and thermal characteristics.This study investigates the compressive mechanical and heat transfer properties of AlSi10Mg gradient metamaterials fabricated by Laser Powder Bed Fusion(LPBF).The morphology of the AlSi10Mg metamaterials was examined using an ultrahigh-resolution microscope.Quasi-static uniaxial compression tests were conducted at room temperature,with deformation behavior captured through camera recordings.The findings indicate that the proposed gradient metamaterial exhibits superior compressive strength properties and energy absorption capacity.The Gradient-SplitP structure demonstrated better compressive performance compared to other strut-based structures,including Gradient-Gyroid and Gradient-Lidinoid structures.With an apparent density of 0.796,the Gradient-SplitP structure exhibited an outstanding energy absorption capacity,reaching an impressive 23.57 MJ/m^(3).In addition,heat conductivity tests were performed to assess the thermal resistance of these structures with different cell configurations.The gradient metamaterials exhibited higher thermal resistance and lower thermal conductivity.Consequently,the designed gradient metamaterials can be considered valuable in various applications,such as thermal management,load-bearing,and energy absorption components.展开更多
Electromagnetic forming tests were done at room temperature to reveal the influence of hydrogen content on the compressive properties of Ti-6Al-4V alloy at high strain rate. Microstructure was observed to reveal the m...Electromagnetic forming tests were done at room temperature to reveal the influence of hydrogen content on the compressive properties of Ti-6Al-4V alloy at high strain rate. Microstructure was observed to reveal the mechanism of hydrogen-enhanced compressive properties. The experimental results indicate that hydrogen has favorable effects on the compressive properties of Ti-6Al-4V alloy at high strain rate. Compression of Ti-6Al-4V alloy first increases up to a maximum and then decreases with the increase of hydrogen content at the same discharge energy under EMF tests. The compression increases by 47.0% when 0.2% (mass fraction) hydrogen is introduced into Ti-6Al-4V alloy. The optimal hydrogen content for cold formation of Ti–6Al–4V alloy under EMF was determined. The reasons for the hydrogen-induced compressive properties were discussed.展开更多
Open-cell nickel foams with different relative densities and pre-stretching degrees were subjected to room temperature quasi-static compressive tests to explore their compressive properties. The compressive properties...Open-cell nickel foams with different relative densities and pre-stretching degrees were subjected to room temperature quasi-static compressive tests to explore their compressive properties. The compressive properties of the nickel foams including yield strength, elastic modulus, energy absorption density and energy absorption efficiency were calculated accurately. The results show that the compressive properties of yield strength, elastic modulus and energy absorption density increase with the increase of relative density of nickel foams. The compressive properties are sensitive to the pre-stretching degree, and the values of yield strength, elastic modulus and energy absorption density decrease with the increase of pre-stretching degree. However, the energy absorption efficiency at the densification strain state exhibits the independence of relative density and pre-stretching degree. The value of energy absorption efficiency reaches its peak when the strain is at the end of the collapse plateau region.展开更多
In our current work,AZ31 magnesium alloy foams with closed-cell were successfully fabricated by melt foaming method using Ca and CaCO3 as thickening and blowing agent,respectively.The influences of porosity and pore s...In our current work,AZ31 magnesium alloy foams with closed-cell were successfully fabricated by melt foaming method using Ca and CaCO3 as thickening and blowing agent,respectively.The influences of porosity and pore size on the quasi-static compressive properties of the foams were systematically investigated.The results showed that the yield strength,energy absorption capacity and ideality energy absorption efficiency were decreased with the increase in porosity.However,specimens with porosities of 60%,65%and 70%possessed similar total energy absorption capacity and ideality energy absorption efficiency.Meanwhile,experimental results showed that mean plateau strength of the foams was increased first and then decreased with increase in mean pore size.In addition,energy absorption capacities were almost the same in the initial stage,while the differences were obvious in the middle stage.From the engineering point of view,the specimens with mean pore size of 1.5 mm possess good combination of mean plateau strength and energy absorption characteristics under the present conditions.展开更多
The effect of the volume fraction of 3D-metal matrix composites(MMC)framework on the compressive properties of 3D interpenetrating hierarchical ZrO_(2)-toughened Al_(2)O_(3)particle(ZTAp)/40Cr steel composites was inv...The effect of the volume fraction of 3D-metal matrix composites(MMC)framework on the compressive properties of 3D interpenetrating hierarchical ZrO_(2)-toughened Al_(2)O_(3)particle(ZTAp)/40Cr steel composites was investigated.The results showed that the compressive properties of the material tended to decrease as the volume fraction of 3D-MMC framework increased.The composite with 35 vol.%3D-MMC had a yield strength of 1455.2 MPa and compressive strength of 1612.8 MPa,which occurred at a strain value of 5.6%.Compared to the homogeneously dispersed composite material,the composite with 35 vol.%3D-MMC had a 144.7%higher yield strength,which occurred at a 20%higher strain.An analysis of the cracks inside the material revealed that the crack was hindered and deflected by the matrix during propagation,which lengthened the crack propagation path and consumed more energy,thus leading to toughening.The results indicated that 3D interpenetrating hierarchical structure had a strengthening and toughening effect on ZTAp/40Cr composites.展开更多
The dynamic mechanical properties of open-cell aluminum alloy foams with different relative densities and cell sizes have been investigated by compressive tests. The strain rates varied from 700 s-1 to 2600 s-1. The e...The dynamic mechanical properties of open-cell aluminum alloy foams with different relative densities and cell sizes have been investigated by compressive tests. The strain rates varied from 700 s-1 to 2600 s-1. The experimental results showed that the dynamic compressive stress-strain curves exhibited a typical three-stage behavior: elastic, plateau and densification. The dynamic compressive strength of foams is affected not only by the relative density but also by the strain rate and cell size. Aluminum alloy foams with higher relative density or smaller cell size are more sensitive to the strain rate than foams with lower relative density or larger cell size.展开更多
As the construction of high-rise building to expand the product line of lightweight concrete. becomes popular, improvement and innovation are required In this paper, two ways of fabricating lightweight concrete were c...As the construction of high-rise building to expand the product line of lightweight concrete. becomes popular, improvement and innovation are required In this paper, two ways of fabricating lightweight concrete were combined to make a new kind of super lightweight concrete. Normal aggregate is replaced with expanded polystyrene （EPS） granule, while foam is introduced to facilitate fabrication process. As a result, super lightweight concrete denoted as EPS foamed concrete is fabricated, whose bulk density is less than 500 kg/m3. Compressive properties of EPS foamed concrete with bulk density 300--500 kg/m3 were investigated by stress-strain curve. It＇s demonstrated that the compressive strength ranges from 0.7 to 2.5 MPa, which is higher than that of similar products. Furthermore, low elastic module and high residual to ultimate strength ratio ensure its excellent deformation and energy absorption capacity. At last, numerical analysis was performed to interpret the inherent variation of elastic modulus and failure mechanism of this material. The results show that EPS foamed concrete is a kind of super lightweight, easy to fabricate material with excellent compressive property and profound utilization potential.展开更多
Ni-50at.%A1 matrix composites containing 0 to 20v.% TiB2 particles have been successfully fabricated by HPES technique. The results show that the Vickers hardness at room temperature and the compressive yield strength...Ni-50at.%A1 matrix composites containing 0 to 20v.% TiB2 particles have been successfully fabricated by HPES technique. The results show that the Vickers hardness at room temperature and the compressive yield strength from room temperature to 1000℃ of the composites increase with increasing volume fraction of the strengthening phase. Especially, the yield strength of NiAl-20TiB2 was approximately twice as high as that of unreinforced NiAl. The ductility of the composites at room temperature is also superior to the monolithic NiAl.展开更多
In the present study, closed-cell aluminum foams with different percentages of erbium （Er） element were successfully prepared. The distribution and existence form of erbium （Er） element and its effect on the compr...In the present study, closed-cell aluminum foams with different percentages of erbium （Er） element were successfully prepared. The distribution and existence form of erbium （Er） element and its effect on the compressive properties of the foams were investigated. Results show that Er uniformly distributes in the cell walls in the forms of Al3Er intermetallic compound and AI-Er solid solutions. Compared with commercially pure aluminum foam, Er-containing foams possess higher micro-hardness, compressive strength and energy absorption capacity due to solid solution strengthening and second phase strengthening effects. Additionally, the amount of Er element should be controlled in the range of 0.10wt.%-0.50wt.% in order to obtain a good combination of compressive strength and energy absorption properties.展开更多
The microstructive and compressive properties of Ti50Al48,Mn2 and Ti50Al48Cr2 alloys are studied in this paper. Existence of x-x+y transformation in TiAl alloys is confirmed by metallographic examination, the transfor...The microstructive and compressive properties of Ti50Al48,Mn2 and Ti50Al48Cr2 alloys are studied in this paper. Existence of x-x+y transformation in TiAl alloys is confirmed by metallographic examination, the transformation temperatures of Ti5()Al48 Mn2 and Ti50Al48Cr2 are 1375 and 1373 C , respectively. After treating within x+y phase field, the microstructure of alloys consists of lamellar zones (I) and bulk rp. The volume ratio of L /rp increases with increasing solution treatment temperature. The third alloying elements of Mn and Cr distribute perferentially over x phase at solution treatment temperatures and result in that x2 and r lamellae become thicker. The yield strength of Ti50Al48Mn2 and Ti50Al48Cr2 alloys decreases and the compressibility increases with increasing rp volume fraction.展开更多
This study investigates the compressive and tensile properties of basalt fiber-reinforced concrete (BFRC) after ultra-low-temperature freeze-thaw cycles. Scanning electron microscope (SEM) analysis was conducted to ex...This study investigates the compressive and tensile properties of basalt fiber-reinforced concrete (BFRC) after ultra-low-temperature freeze-thaw cycles. Scanning electron microscope (SEM) analysis was conducted to examine the deterioration mechanisms caused by freeze-thaw cycles and sulfate erosion. The results show that compressive and tensile strengths increase with basalt fiber dosage. The optimal dosage is 0.2%. With longer exposure to sulfate erosion, both strengths decline significantly. Basalt fibers effectively bridge cracks, control expansion, enhance compactness, and improve concrete performance. Ultra-low-temperature freeze-thaw cycles and sulfate erosion cause rapid crack growth. Sulfate erosion produces crystallization products and expansive substances. These fill cracks, create pressure, and damage the internal structure. Freezing and expansion forces further enlarge voids and cracks. This provides space for expansive substances, worsening concrete deterioration and reducing its performance.展开更多
The compressive properties of the aluminum matrix composite reinforced with 55% B4C （volume fraction） particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress--strai...The compressive properties of the aluminum matrix composite reinforced with 55% B4C （volume fraction） particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress--strain curves were obtained at the temperature ranging from 298 to 773 K and strain rate ranging from 1×10^（-3） to 5 s ^（-1）. The results showed that the dynamic compressive strength decreased more slowly than the quasi-static compressive strength at elevated temperatures, which was attributed to the different failure modes of the composite under dynamic and quasi-static load. The strain rate sensitivity increased from 0.02 to 0.13 when the temperature increased from room temperature to 773 K, suggesting that the strain rate sensitivity of this type of composite is a function of temperature.展开更多
Semi open-cell aluminum foams having channels between individual cells were produced using low cost CaCO3foamingagent and applying the powder compact melting process.To this end,the aluminum and CaCO3powder mixtures w...Semi open-cell aluminum foams having channels between individual cells were produced using low cost CaCO3foamingagent and applying the powder compact melting process.To this end,the aluminum and CaCO3powder mixtures were coldcompacted into dense cylindrical precursors for foaming at specific temperatures under air atmosphere.The effects of severalparameters including precursor compaction pressure,foaming agent content as well as temperature and time of the foaming processon the cell microstructure,linear expansion,relative density and compressive properties were investigated.A uniform distribution ofcells with sizes less than100μm,which form semi open-cell structures with relative densities in the range of55.4%-84.4%,wasobtained.The elevation of compaction pressure between127-318MPa and blowing agent up to15%(mass fraction)led to anincrease in the linear expansion,compressive strength and densification strain.By varying the foaming temperature from800to1000°C,all of the investigated parameters increased except compressive strength and relative density.The results indicated theoptimal foaming temperature and time as900°C and10-25min,respectively.展开更多
In the present work,Fe–Mn–Al–C powder mixtures were manufactured by elemental powders with different ball milling time,and the porous high-Mn and high-Al steel was fabricated by powder sintering.The results indicat...In the present work,Fe–Mn–Al–C powder mixtures were manufactured by elemental powders with different ball milling time,and the porous high-Mn and high-Al steel was fabricated by powder sintering.The results indicated that the powder size significantly decreased,and the morphology of the Fe powder tended to be increasingly flat as the milling time increased.However,the prolonged milling duration had limited impact on the phase transition of the powder mixture.The main phases of all the samples sintered at 640℃ were α-Fe,α-Mn and Al,and a small amount of Fe2Al5 and Al8Mn5.When the sintering temperature increased to 1200℃,the phase composition was mainly comprised of γ-Fe and α-Fe.The weight loss fraction of the sintered sample decreased with milling time,i.e.,8.3wt% after 20 h milling compared to15.3wt% for 10 h.The Mn depletion region(MDR) for the 10,15,and 20 h milled samples was about 780,600,and 370 μm,respectively.The total porosity of samples sintered at 640℃ decreased from ~46.6vol% for the 10 h milled powder to ~44.2vol% for 20 h milled powder.After sintering at 1200℃,the total porosity of sintered samples prepared by 10 and 20 h milled powder was ~58.3vol% and ~51.3vol%,respectively.The compressive strength and ductility of the 1200℃ sintered porous steel increased as the milling time increased.展开更多
Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressiv...Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressive strength of the composites were measured.The effects of mass fraction of cenospheres on the microstructure and compressive properties were characterized.The results show that the cenospheres are uniformly distributed in the matrix and there is no sign of cenosphere cluster or residual pore.The densities of the composites are 1.85-1.92 g/cm 3 .By comparing with matrix,the compressive yield strength of the composites is improved,and the cenospheres is filled with Mg matrix alloy.SEM,XRD and EDX results of the composites show clear evidence of reaction product at cenosphere/matrix interface.On the basis of XRD and EDX,composition, structure and thermodynamic analysis,the main interfacial phase between the cenosphere and AZ91D Mg alloy was identified to be MgAl2O4.展开更多
The dynamic mechanical properties of basalt affected by microwave were investigated by performing dynamic compressive tests using the SHPB system.Meanwhile,the thermal damage of the treated basalt was characterized by...The dynamic mechanical properties of basalt affected by microwave were investigated by performing dynamic compressive tests using the SHPB system.Meanwhile,the thermal damage of the treated basalt was characterized by ultrasonic non-destructive testing and nuclear magnetic resonance technology.The results show that with the increase of microwave power and exposure time,the P-wave velocity,dynamic compressive strength and elastic modulus decrease continuously,and the dynamic failure mode tends to be a more complex fracturing.The increase in microwave power and exposure time can enhance the temperature difference and transfer coefficient among minerals,hence intensifying the rock damage induced by thermal shock.展开更多
Microwave processing was used to cure the carbon fiber/epoxy composites and designed for improving the compressive strength of the materials. By controlling the power of microwave heating, vacuum bagged laminates were...Microwave processing was used to cure the carbon fiber/epoxy composites and designed for improving the compressive strength of the materials. By controlling the power of microwave heating, vacuum bagged laminates were fabricated under one atmosphere pressure without arcing. The physical and mechanical properties of composites produced through vacuum bagging using microwave and thermal curing were compared and the multistep （2-step or 3-step） microwave curing process for improved compressive properties was established. The results indicated that microwave cured samples had somewhat differentiated molecular structure and showed slightly higher glass transition temperature. The 2-step process was found to be more conducive to the enhancement of the compressive strength than the 3-step process. A 39% cure cycle time reduction and a 22% compressive strength increment were achieved for the composites manufactured with microwave radiation. The improvement in specific compressive strength was attributed to better interracial bonding between resin matrix and the fibers, which was also demonstrated via scanning electron microscopy analysis.展开更多
基金The authors would like to acknowledge the financial support from the National Key Basic Research Program(973 Program),Project(2013CB632205).
文摘For the purpose of investigating the dynamic deformational behavior and failure mechanisms of magnesium under high strain rates,the Split Hopkinson Pressure Bar(SHPB)was used for investigating dynamic mechanical properties of extruded Mg-Gd-Y Magnesium alloy at ambient temperature(300 K),200℃(473 K)and 300℃(573 K)temperature.The samples after compression were analyzed by scanning electron microscope(SEM)and metallographic microscope.Dynamic mechanical properties,crack performance and plastic deformation mechanism of extruded Mg-Gd-Y Magnesium alloy along the extrusion direction(ED)were discussed.The results show that,extruded Mg-Gd-Y Magnesium alloy has the largest dynamic compressive strength which is 535 MPa at ambient temperature(300 K)and strain rate of 2826 s^(−1).When temperature increases,dynamic compressive strength decreases,while ductility increases.The dynamic compression fracture mechanism of extruded Mg-Gd-Y Magnesium alloy is multi-crack propagation and intergranular quasi-cleavage fracture at both ambient temperature and high temperature.The dynamic compressive deformation mechanism of extruded Mg-Gd-Y Magnesium alloy is a combination of twinning,slipping and dynamic recrystallization at both ambient temperature and high temperature.
文摘A combination of hard(SiCP)and soft(fly ash)particulate reinforcements could be a strategy to enhance combination of multiple properties of Magnesium and its alloys which otherwise suffer from low stiffness,low wear resistance,and many other critical properties.However,at present a comprehensive and robust map correlating different properties in particle-reinforced composites is much lacking.In this work,an industrial grade AZ91 magnesium alloy reinforced with hard SiC and soft fly ash particles(with 3 vol.%each),has been prepared using stir casting followed by hot extrusion at 325℃with a ratio of 21.5.Microstructure of the hybrid composite was characterized using optical and scanning electron microscopes.The composite exhibited a reduction in average grain size from 13.6 to 7.1μm,concomitantly an increase in Vickers hardness from 73 to 111 HV.The tension-compression yield asymmetry ratios of the unreinforced alloy and hybrid composite were 1.165 and 0.976,respectively indicating higher yield strength for the composite under compressive load.The composite exhibited 76%improvement in damping capacity under time sweep mode,and 28%improvement at 423 K under temperature sweep mode.The tribological characteristics of the composite under dry sliding conditions at sliding speeds and loads in the range of 0.5 to 1.5 m s^(-1)and 10 to 30 N,respectively showed higher wear resistance than the unreinforced alloy.The composite showed 23%improvement in sliding wear resistance at a load of 20 N and a speed of 1 m s^(-1).Finally,efforts have been made to understand the influence of one property on the other by developing statistical property correlation maps from the properties obtained in this study and from the literature.These maps are expected to help in the design of hybrid Metal Matrix Composites for a variety of targeted applications in different sectors.
基金support from the National Natural Science Foundation of China (No.52231004,52175365,51972271)Dr.Jiawei Fu appreciates the support from The Young Talents Plan in Shaanxi Province of China (No.00121)。
文摘To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex configuration features and abrupt cross-sectional transitions was fabricated by liquid-solid extrusion following vacuum pressure infiltration process(LSEVI).Near-net forming schemes of both the special-shaped fiber preform and composite part were proposed.The effect of process parameters on the forming quality of the composite part was discussed.Meanwhile,the microstructures and compressive properties in different regions of the part were analyzed.The results show that the forward forming scheme provides the special-shaped fiber preform with no surface defects.For the C_(sf)/AZ91D part,its internal microstructures show that the infiltration of liquid magnesium is sufficient and uniform.The compressive strength of the composite part can reach up to 487 MPa,corresponding to~40%increase compared to 335 MPa of the AZ91D alloy.The average compressive strain of composites is less than 10%,which is about 50%of that of the AZ91D alloy.When the fiber orientation is parallel to the shear direction on the shear plane,the load-bearing capacity of the fiber is much higher than that of the fiber perpendicular to the shear direction.This work not only provides a convenient approach to fabricate special-shaped preform with high fiber volume fraction,but also gives a demonstration for the near-net forming of C_(sf)/Mg parts with excellent material isotropy and compressive properties.
基金Supported by National Natural Science Foundation of China(Grant No.12272045)the BIT Research and Innovation Promoting Project(Grant No.2023YCXZ025).
文摘Metamaterials are defined as artificially designed micro-architectures with unusual physical properties,including optical,electromagnetic,mechanical,and thermal characteristics.This study investigates the compressive mechanical and heat transfer properties of AlSi10Mg gradient metamaterials fabricated by Laser Powder Bed Fusion(LPBF).The morphology of the AlSi10Mg metamaterials was examined using an ultrahigh-resolution microscope.Quasi-static uniaxial compression tests were conducted at room temperature,with deformation behavior captured through camera recordings.The findings indicate that the proposed gradient metamaterial exhibits superior compressive strength properties and energy absorption capacity.The Gradient-SplitP structure demonstrated better compressive performance compared to other strut-based structures,including Gradient-Gyroid and Gradient-Lidinoid structures.With an apparent density of 0.796,the Gradient-SplitP structure exhibited an outstanding energy absorption capacity,reaching an impressive 23.57 MJ/m^(3).In addition,heat conductivity tests were performed to assess the thermal resistance of these structures with different cell configurations.The gradient metamaterials exhibited higher thermal resistance and lower thermal conductivity.Consequently,the designed gradient metamaterials can be considered valuable in various applications,such as thermal management,load-bearing,and energy absorption components.
基金Project (51205102) supported by the National Natural Science Foundation of ChinaProject (2012M511401) supported by the China Postdoctoral Science FoundationProject (gf201101001) supported by the National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology, Nanchang Hangkong University, China
文摘Electromagnetic forming tests were done at room temperature to reveal the influence of hydrogen content on the compressive properties of Ti-6Al-4V alloy at high strain rate. Microstructure was observed to reveal the mechanism of hydrogen-enhanced compressive properties. The experimental results indicate that hydrogen has favorable effects on the compressive properties of Ti-6Al-4V alloy at high strain rate. Compression of Ti-6Al-4V alloy first increases up to a maximum and then decreases with the increase of hydrogen content at the same discharge energy under EMF tests. The compression increases by 47.0% when 0.2% (mass fraction) hydrogen is introduced into Ti-6Al-4V alloy. The optimal hydrogen content for cold formation of Ti–6Al–4V alloy under EMF was determined. The reasons for the hydrogen-induced compressive properties were discussed.
基金Project supported by the 2015 Shandong Province Project of Outstanding Subject Talent Group
文摘Open-cell nickel foams with different relative densities and pre-stretching degrees were subjected to room temperature quasi-static compressive tests to explore their compressive properties. The compressive properties of the nickel foams including yield strength, elastic modulus, energy absorption density and energy absorption efficiency were calculated accurately. The results show that the compressive properties of yield strength, elastic modulus and energy absorption density increase with the increase of relative density of nickel foams. The compressive properties are sensitive to the pre-stretching degree, and the values of yield strength, elastic modulus and energy absorption density decrease with the increase of pre-stretching degree. However, the energy absorption efficiency at the densification strain state exhibits the independence of relative density and pre-stretching degree. The value of energy absorption efficiency reaches its peak when the strain is at the end of the collapse plateau region.
基金The present authors thanks to the financial support provided by International Science&Technology Cooperation Program of China(2010DFA51850)“863”project of China(NO.2013AA031002),Major Project of China(2013ZX04004027)+3 种基金the‘100 Talents Project’of Hebei Province of China(Grant No.E2012100009)Natural Science Foundation of Hebei Province of China(No.E2012202017)Science and Technology Project of Hebei Province(13211008D)Science and Technology Research of Hebei Province for Youth fund(No.2011182).
文摘In our current work,AZ31 magnesium alloy foams with closed-cell were successfully fabricated by melt foaming method using Ca and CaCO3 as thickening and blowing agent,respectively.The influences of porosity and pore size on the quasi-static compressive properties of the foams were systematically investigated.The results showed that the yield strength,energy absorption capacity and ideality energy absorption efficiency were decreased with the increase in porosity.However,specimens with porosities of 60%,65%and 70%possessed similar total energy absorption capacity and ideality energy absorption efficiency.Meanwhile,experimental results showed that mean plateau strength of the foams was increased first and then decreased with increase in mean pore size.In addition,energy absorption capacities were almost the same in the initial stage,while the differences were obvious in the middle stage.From the engineering point of view,the specimens with mean pore size of 1.5 mm possess good combination of mean plateau strength and energy absorption characteristics under the present conditions.
基金supported by the National Natural Science Foundation of China(No.51461025).
文摘The effect of the volume fraction of 3D-metal matrix composites(MMC)framework on the compressive properties of 3D interpenetrating hierarchical ZrO_(2)-toughened Al_(2)O_(3)particle(ZTAp)/40Cr steel composites was investigated.The results showed that the compressive properties of the material tended to decrease as the volume fraction of 3D-MMC framework increased.The composite with 35 vol.%3D-MMC had a yield strength of 1455.2 MPa and compressive strength of 1612.8 MPa,which occurred at a strain value of 5.6%.Compared to the homogeneously dispersed composite material,the composite with 35 vol.%3D-MMC had a 144.7%higher yield strength,which occurred at a 20%higher strain.An analysis of the cracks inside the material revealed that the crack was hindered and deflected by the matrix during propagation,which lengthened the crack propagation path and consumed more energy,thus leading to toughening.The results indicated that 3D interpenetrating hierarchical structure had a strengthening and toughening effect on ZTAp/40Cr composites.
基金This work was supported by the Natural Science Foundation of CAEP under grant No.10076020.
文摘The dynamic mechanical properties of open-cell aluminum alloy foams with different relative densities and cell sizes have been investigated by compressive tests. The strain rates varied from 700 s-1 to 2600 s-1. The experimental results showed that the dynamic compressive stress-strain curves exhibited a typical three-stage behavior: elastic, plateau and densification. The dynamic compressive strength of foams is affected not only by the relative density but also by the strain rate and cell size. Aluminum alloy foams with higher relative density or smaller cell size are more sensitive to the strain rate than foams with lower relative density or larger cell size.
基金the National Natural Science Foundation of China(No.50708059)the Open Fund of Key Laboratory of Advanced Civil Engineering Materials (Tongji University),Ministry of Education (No.K201002)
文摘As the construction of high-rise building to expand the product line of lightweight concrete. becomes popular, improvement and innovation are required In this paper, two ways of fabricating lightweight concrete were combined to make a new kind of super lightweight concrete. Normal aggregate is replaced with expanded polystyrene （EPS） granule, while foam is introduced to facilitate fabrication process. As a result, super lightweight concrete denoted as EPS foamed concrete is fabricated, whose bulk density is less than 500 kg/m3. Compressive properties of EPS foamed concrete with bulk density 300--500 kg/m3 were investigated by stress-strain curve. It＇s demonstrated that the compressive strength ranges from 0.7 to 2.5 MPa, which is higher than that of similar products. Furthermore, low elastic module and high residual to ultimate strength ratio ensure its excellent deformation and energy absorption capacity. At last, numerical analysis was performed to interpret the inherent variation of elastic modulus and failure mechanism of this material. The results show that EPS foamed concrete is a kind of super lightweight, easy to fabricate material with excellent compressive property and profound utilization potential.
文摘Ni-50at.%A1 matrix composites containing 0 to 20v.% TiB2 particles have been successfully fabricated by HPES technique. The results show that the Vickers hardness at room temperature and the compressive yield strength from room temperature to 1000℃ of the composites increase with increasing volume fraction of the strengthening phase. Especially, the yield strength of NiAl-20TiB2 was approximately twice as high as that of unreinforced NiAl. The ductility of the composites at room temperature is also superior to the monolithic NiAl.
基金supported by the National Natural Science Foundation of China(No.51501053 and 51475138)Science and Technology Plan Projects of Hebei Province(No.15211026)
文摘In the present study, closed-cell aluminum foams with different percentages of erbium （Er） element were successfully prepared. The distribution and existence form of erbium （Er） element and its effect on the compressive properties of the foams were investigated. Results show that Er uniformly distributes in the cell walls in the forms of Al3Er intermetallic compound and AI-Er solid solutions. Compared with commercially pure aluminum foam, Er-containing foams possess higher micro-hardness, compressive strength and energy absorption capacity due to solid solution strengthening and second phase strengthening effects. Additionally, the amount of Er element should be controlled in the range of 0.10wt.%-0.50wt.% in order to obtain a good combination of compressive strength and energy absorption properties.
文摘The microstructive and compressive properties of Ti50Al48,Mn2 and Ti50Al48Cr2 alloys are studied in this paper. Existence of x-x+y transformation in TiAl alloys is confirmed by metallographic examination, the transformation temperatures of Ti5()Al48 Mn2 and Ti50Al48Cr2 are 1375 and 1373 C , respectively. After treating within x+y phase field, the microstructure of alloys consists of lamellar zones (I) and bulk rp. The volume ratio of L /rp increases with increasing solution treatment temperature. The third alloying elements of Mn and Cr distribute perferentially over x phase at solution treatment temperatures and result in that x2 and r lamellae become thicker. The yield strength of Ti50Al48Mn2 and Ti50Al48Cr2 alloys decreases and the compressibility increases with increasing rp volume fraction.
文摘This study investigates the compressive and tensile properties of basalt fiber-reinforced concrete (BFRC) after ultra-low-temperature freeze-thaw cycles. Scanning electron microscope (SEM) analysis was conducted to examine the deterioration mechanisms caused by freeze-thaw cycles and sulfate erosion. The results show that compressive and tensile strengths increase with basalt fiber dosage. The optimal dosage is 0.2%. With longer exposure to sulfate erosion, both strengths decline significantly. Basalt fibers effectively bridge cracks, control expansion, enhance compactness, and improve concrete performance. Ultra-low-temperature freeze-thaw cycles and sulfate erosion cause rapid crack growth. Sulfate erosion produces crystallization products and expansive substances. These fill cracks, create pressure, and damage the internal structure. Freezing and expansion forces further enlarge voids and cracks. This provides space for expansive substances, worsening concrete deterioration and reducing its performance.
文摘The compressive properties of the aluminum matrix composite reinforced with 55% B4C （volume fraction） particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress--strain curves were obtained at the temperature ranging from 298 to 773 K and strain rate ranging from 1×10^（-3） to 5 s ^（-1）. The results showed that the dynamic compressive strength decreased more slowly than the quasi-static compressive strength at elevated temperatures, which was attributed to the different failure modes of the composite under dynamic and quasi-static load. The strain rate sensitivity increased from 0.02 to 0.13 when the temperature increased from room temperature to 773 K, suggesting that the strain rate sensitivity of this type of composite is a function of temperature.
文摘Semi open-cell aluminum foams having channels between individual cells were produced using low cost CaCO3foamingagent and applying the powder compact melting process.To this end,the aluminum and CaCO3powder mixtures were coldcompacted into dense cylindrical precursors for foaming at specific temperatures under air atmosphere.The effects of severalparameters including precursor compaction pressure,foaming agent content as well as temperature and time of the foaming processon the cell microstructure,linear expansion,relative density and compressive properties were investigated.A uniform distribution ofcells with sizes less than100μm,which form semi open-cell structures with relative densities in the range of55.4%-84.4%,wasobtained.The elevation of compaction pressure between127-318MPa and blowing agent up to15%(mass fraction)led to anincrease in the linear expansion,compressive strength and densification strain.By varying the foaming temperature from800to1000°C,all of the investigated parameters increased except compressive strength and relative density.The results indicated theoptimal foaming temperature and time as900°C and10-25min,respectively.
基金financially supported by the National Key R&D Program of China(No.2021YFB3802300)the National Natural Science Foundation of China(No.51804239)Guangdong Major Project of Basic and Applied Basic Research,China(No.2021B0301030001)。
文摘In the present work,Fe–Mn–Al–C powder mixtures were manufactured by elemental powders with different ball milling time,and the porous high-Mn and high-Al steel was fabricated by powder sintering.The results indicated that the powder size significantly decreased,and the morphology of the Fe powder tended to be increasingly flat as the milling time increased.However,the prolonged milling duration had limited impact on the phase transition of the powder mixture.The main phases of all the samples sintered at 640℃ were α-Fe,α-Mn and Al,and a small amount of Fe2Al5 and Al8Mn5.When the sintering temperature increased to 1200℃,the phase composition was mainly comprised of γ-Fe and α-Fe.The weight loss fraction of the sintered sample decreased with milling time,i.e.,8.3wt% after 20 h milling compared to15.3wt% for 10 h.The Mn depletion region(MDR) for the 10,15,and 20 h milled samples was about 780,600,and 370 μm,respectively.The total porosity of samples sintered at 640℃ decreased from ~46.6vol% for the 10 h milled powder to ~44.2vol% for 20 h milled powder.After sintering at 1200℃,the total porosity of sintered samples prepared by 10 and 20 h milled powder was ~58.3vol% and ~51.3vol%,respectively.The compressive strength and ductility of the 1200℃ sintered porous steel increased as the milling time increased.
基金Project(2007KZ07)supported by Plans for Science and Technology of Changchun City,ChinaProject supported by the Program for New Century Excellent Talents in University,ChinaProject supported by the 985 Project of Jilin University,China
文摘Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressive strength of the composites were measured.The effects of mass fraction of cenospheres on the microstructure and compressive properties were characterized.The results show that the cenospheres are uniformly distributed in the matrix and there is no sign of cenosphere cluster or residual pore.The densities of the composites are 1.85-1.92 g/cm 3 .By comparing with matrix,the compressive yield strength of the composites is improved,and the cenospheres is filled with Mg matrix alloy.SEM,XRD and EDX results of the composites show clear evidence of reaction product at cenosphere/matrix interface.On the basis of XRD and EDX,composition, structure and thermodynamic analysis,the main interfacial phase between the cenosphere and AZ91D Mg alloy was identified to be MgAl2O4.
基金supported by the National Natural Science Foundation of China(Nos.51774325,41972283,11972378).
文摘The dynamic mechanical properties of basalt affected by microwave were investigated by performing dynamic compressive tests using the SHPB system.Meanwhile,the thermal damage of the treated basalt was characterized by ultrasonic non-destructive testing and nuclear magnetic resonance technology.The results show that with the increase of microwave power and exposure time,the P-wave velocity,dynamic compressive strength and elastic modulus decrease continuously,and the dynamic failure mode tends to be a more complex fracturing.The increase in microwave power and exposure time can enhance the temperature difference and transfer coefficient among minerals,hence intensifying the rock damage induced by thermal shock.
基金the Innovation Funds of China-National Engineering and Research Center for Commercial Aircraft Manufacturing (SAMC12-JS-15-015) for financial support
文摘Microwave processing was used to cure the carbon fiber/epoxy composites and designed for improving the compressive strength of the materials. By controlling the power of microwave heating, vacuum bagged laminates were fabricated under one atmosphere pressure without arcing. The physical and mechanical properties of composites produced through vacuum bagging using microwave and thermal curing were compared and the multistep （2-step or 3-step） microwave curing process for improved compressive properties was established. The results indicated that microwave cured samples had somewhat differentiated molecular structure and showed slightly higher glass transition temperature. The 2-step process was found to be more conducive to the enhancement of the compressive strength than the 3-step process. A 39% cure cycle time reduction and a 22% compressive strength increment were achieved for the composites manufactured with microwave radiation. The improvement in specific compressive strength was attributed to better interracial bonding between resin matrix and the fibers, which was also demonstrated via scanning electron microscopy analysis.
