Outstanding mechanical properties of graphene nanoplatelets(GNPs)make them ideal reinforcement for mass production of composites.In this research,the composites were fabricated by stir-casting method.GNPs were added i...Outstanding mechanical properties of graphene nanoplatelets(GNPs)make them ideal reinforcement for mass production of composites.In this research,the composites were fabricated by stir-casting method.GNPs were added in 1.5 and 3.0 wt.%into Mg–3wt.%Al–1wt.%Zn(AZ31)magnesium alloy.As cast ingots were preheated for one hour and extruded at 350℃ with extrusion ratio of 5.2:1.As extruded AZ31-GNPs composites were micro-structurally characterized with X-ray diffraction,optical microscopy and scanning electron microscopy.Vickers microhardness of synthesized materials was investigated both in parallel and perpendicular to extrusion directions.Room temperature mechanical testing revealed that with increasing GNP’s content,tensile fracture strain was remarkably increased without significant compromise in tensile strength.Furthermore,as extruded AZ31-3GNPs composites were subjected to tensile testing at temperatures ranging from 75℃ to 300℃ with initial strain rate of 2×10^(−3)s^(−1) to evaluate high temperature formability of composite.It was found that like CNTs,GNPs also have the potential to sustain tensile strength at high temperatures.展开更多
In this research,microstructure evaluation,mechanical properties and thermal conductivity of the Mg-SiC_(w)/Cu composite with laminar structure were investigated.For this purpose,SiC whiskers were added to magnesium a...In this research,microstructure evaluation,mechanical properties and thermal conductivity of the Mg-SiC_(w)/Cu composite with laminar structure were investigated.For this purpose,SiC whiskers were added to magnesium alloy by using stir-casting,then the Mg-SiC_(w)composite was bonded to copper layers by warm accumulative roll bonding(ARB).Based on the results of optical microscopy(OM)and scanning electron microscopy(SEM),SiC whiskers were well distributed in the magnesium matrix and they were aligned parallelly when the composites were plastically deformed at higher rolling passes.Furthermore,all layers remained continuous with localized necking sites.Also,no intermetallic compounds and phases were detected by XRD and EDS analyzes.Apart from the significant effect of severe plastic deformation on mechanical properties,the findings of mechanical tests point to the usefulness of reinforcements in improving up to 60%microhardness,Young’s modulus,yield,and up to 41%tensile strengths.Further,thermal conductivities of composites increased by adding reinforcement and above all by increasing the number of rolling passes.This growth is attributed to the higher thermal diffusivity of copper and whiskers as well as the increased number of conductive layers within composite.展开更多
Aluminum based metal matrix composites were fabricated using stir casting where silicon carbide and alumina were the reinforcements. Different types of properties (physical-density, mechanical-tensile, hardness, chemi...Aluminum based metal matrix composites were fabricated using stir casting where silicon carbide and alumina were the reinforcements. Different types of properties (physical-density, mechanical-tensile, hardness, chemical-corrosion etc.) were measured and compared with base metals/alloys. The properties were significantly varied. The highest density was obtained for pure aluminium with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-4032 alloy. The highest hardness was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for pure Al with 5% Al<sub>2</sub>O<sub>3</sub>. The highest strength was obtained for AA-6061 with 5% coarse SiC whereas the lowest was obtained for pure Al. The highest impact strength was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-6061. The corrosion resistance of all composites was lower than that of the base materials.展开更多
The present study investigates the effect of WC nano-particles on tribological behavior of magnesium based nanocomposites for varying wt%of WC(0.5,1,1.5 and 2 wt%).Nanocomposites are fabricated using ultrasonic vibrat...The present study investigates the effect of WC nano-particles on tribological behavior of magnesium based nanocomposites for varying wt%of WC(0.5,1,1.5 and 2 wt%).Nanocomposites are fabricated using ultrasonic vibration assisted stir casting method.Optical microscopy,scanning electron microscopy and energy dispersive x-ray patterns are used to characterize the base alloy and fabricated composites.Microhardness values of as-cast composites are obtained through Vicker’s micro-hardness tester.Friction and wear behavior of fabricated composites are studied using pin-on-disk type tribotester at room temperature under dry sliding condition.Operating load range is 10-40 N while sliding speed range is 0.1-0.4 m/s.Characterization of Mg-composites confirms particle inclusion as well as better microstructural integrity with increase in reinforcement.Hardness value of composites increases with increase in the amount of WC nano-particles.Wear and friction behavior of base matrix are also enhanced due to incorporation of WC nano-particles.Different wear mechanisms occurring at the contact surfaces are ascertained through SEM images and EDAX patterns.Oxidation in the tested surface is also identified through SEM and EDAX.This yields better tribological behavior in composites.展开更多
Al-7075 alloy-base matrix, reinforced with mixtures of silicon carbide (SiC) and boron carbide (B4C) particles, know as hybrid composites have been fabricated by stir casting technique (liquid metallurgy route) and op...Al-7075 alloy-base matrix, reinforced with mixtures of silicon carbide (SiC) and boron carbide (B4C) particles, know as hybrid composites have been fabricated by stir casting technique (liquid metallurgy route) and optimized at different parameters like sliding speed, applied load, sliding time, and percentage of reinforcement by Taguchi method. The specimens were examined by Rockwell hardness test machine, Pin on Disc, Scanning Electron Microscope (SEM) and Optical Microscope. A plan of experiment generated through Taguchi’s technique is used to conduct experiments based on L27 orthogonal array. The developed ANOVA and the regression equations were used to find the optimum wear as well as co-efficient of friction under the influence of sliding speed, applied load, sliding time and percentage of reinforcement. The dry sliding wear resistance was analyzed on the basis of “smaller the best”. Finally, confirmation tests were carried out to verify the experimental results.展开更多
基金the National Natural Science Foundation of China(Projects 51531002,51474043,51571043)Fundamental Research Funds for the Central Universities(Grant 106112015CDJZR135515)Chongqing Municipal Government(CSTC2013JCYJC60001,CEC project,Two River Scholar Project andThe Chief Scientist Studio Project).
文摘Outstanding mechanical properties of graphene nanoplatelets(GNPs)make them ideal reinforcement for mass production of composites.In this research,the composites were fabricated by stir-casting method.GNPs were added in 1.5 and 3.0 wt.%into Mg–3wt.%Al–1wt.%Zn(AZ31)magnesium alloy.As cast ingots were preheated for one hour and extruded at 350℃ with extrusion ratio of 5.2:1.As extruded AZ31-GNPs composites were micro-structurally characterized with X-ray diffraction,optical microscopy and scanning electron microscopy.Vickers microhardness of synthesized materials was investigated both in parallel and perpendicular to extrusion directions.Room temperature mechanical testing revealed that with increasing GNP’s content,tensile fracture strain was remarkably increased without significant compromise in tensile strength.Furthermore,as extruded AZ31-3GNPs composites were subjected to tensile testing at temperatures ranging from 75℃ to 300℃ with initial strain rate of 2×10^(−3)s^(−1) to evaluate high temperature formability of composite.It was found that like CNTs,GNPs also have the potential to sustain tensile strength at high temperatures.
文摘In this research,microstructure evaluation,mechanical properties and thermal conductivity of the Mg-SiC_(w)/Cu composite with laminar structure were investigated.For this purpose,SiC whiskers were added to magnesium alloy by using stir-casting,then the Mg-SiC_(w)composite was bonded to copper layers by warm accumulative roll bonding(ARB).Based on the results of optical microscopy(OM)and scanning electron microscopy(SEM),SiC whiskers were well distributed in the magnesium matrix and they were aligned parallelly when the composites were plastically deformed at higher rolling passes.Furthermore,all layers remained continuous with localized necking sites.Also,no intermetallic compounds and phases were detected by XRD and EDS analyzes.Apart from the significant effect of severe plastic deformation on mechanical properties,the findings of mechanical tests point to the usefulness of reinforcements in improving up to 60%microhardness,Young’s modulus,yield,and up to 41%tensile strengths.Further,thermal conductivities of composites increased by adding reinforcement and above all by increasing the number of rolling passes.This growth is attributed to the higher thermal diffusivity of copper and whiskers as well as the increased number of conductive layers within composite.
文摘Aluminum based metal matrix composites were fabricated using stir casting where silicon carbide and alumina were the reinforcements. Different types of properties (physical-density, mechanical-tensile, hardness, chemical-corrosion etc.) were measured and compared with base metals/alloys. The properties were significantly varied. The highest density was obtained for pure aluminium with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-4032 alloy. The highest hardness was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for pure Al with 5% Al<sub>2</sub>O<sub>3</sub>. The highest strength was obtained for AA-6061 with 5% coarse SiC whereas the lowest was obtained for pure Al. The highest impact strength was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-6061. The corrosion resistance of all composites was lower than that of the base materials.
基金We gratefully acknowledge the support of DST sponsored Smart Foundry-2020 program of Jadavpur University .
文摘The present study investigates the effect of WC nano-particles on tribological behavior of magnesium based nanocomposites for varying wt%of WC(0.5,1,1.5 and 2 wt%).Nanocomposites are fabricated using ultrasonic vibration assisted stir casting method.Optical microscopy,scanning electron microscopy and energy dispersive x-ray patterns are used to characterize the base alloy and fabricated composites.Microhardness values of as-cast composites are obtained through Vicker’s micro-hardness tester.Friction and wear behavior of fabricated composites are studied using pin-on-disk type tribotester at room temperature under dry sliding condition.Operating load range is 10-40 N while sliding speed range is 0.1-0.4 m/s.Characterization of Mg-composites confirms particle inclusion as well as better microstructural integrity with increase in reinforcement.Hardness value of composites increases with increase in the amount of WC nano-particles.Wear and friction behavior of base matrix are also enhanced due to incorporation of WC nano-particles.Different wear mechanisms occurring at the contact surfaces are ascertained through SEM images and EDAX patterns.Oxidation in the tested surface is also identified through SEM and EDAX.This yields better tribological behavior in composites.
文摘Al-7075 alloy-base matrix, reinforced with mixtures of silicon carbide (SiC) and boron carbide (B4C) particles, know as hybrid composites have been fabricated by stir casting technique (liquid metallurgy route) and optimized at different parameters like sliding speed, applied load, sliding time, and percentage of reinforcement by Taguchi method. The specimens were examined by Rockwell hardness test machine, Pin on Disc, Scanning Electron Microscope (SEM) and Optical Microscope. A plan of experiment generated through Taguchi’s technique is used to conduct experiments based on L27 orthogonal array. The developed ANOVA and the regression equations were used to find the optimum wear as well as co-efficient of friction under the influence of sliding speed, applied load, sliding time and percentage of reinforcement. The dry sliding wear resistance was analyzed on the basis of “smaller the best”. Finally, confirmation tests were carried out to verify the experimental results.
