A surface Ti-WC composite was fabricated on CP-Ti by surface friction stirring(SFS)using a pinless WC-Cotool at a processing window of 800−2500 r/min and 8−50 mm/min.At 1600 r/min-50 mm/min,a defect-free compositelaye...A surface Ti-WC composite was fabricated on CP-Ti by surface friction stirring(SFS)using a pinless WC-Cotool at a processing window of 800−2500 r/min and 8−50 mm/min.At 1600 r/min-50 mm/min,a defect-free compositelayer with an average hardness of~HV 1170 is formed.The hardness was increased by WC and TiN reinforcingparticles,dissolved Co atoms in Ti,and the formation of ultrafine grains.WC particles were incorporated into the Tisubstrate owing to the intense frictional interaction/heating at the tool-plate interface(~1000℃),which led to strengthloss and wear of the tool.The Williamson-Hall analysis of the XRD peaks of the SFSed sample confirmed a significantlysmall crystallite size(~100 nm).Wear tests showed that the wear resistance of the composite structure was about 4.5times higher than that of the CP-Ti.Friction analysis revealed a significant reduction in average value and fluctuations ofthe friction coefficient.展开更多
The aim of present study is to analyze the influence of volume percentage(vol.%) of nano-sized particles(TiB_2: average size is 35 nm) on microstructure, mechanical and tribological behavior of 6061-T6 Al alloy surfac...The aim of present study is to analyze the influence of volume percentage(vol.%) of nano-sized particles(TiB_2: average size is 35 nm) on microstructure, mechanical and tribological behavior of 6061-T6 Al alloy surface nano composite prepared via Friction stir process(FSP). The microstructure of the fabricated surface nanocomposites is examined using optical microscopy(OM) and scanning electron microscope(SEM) for distribution of TiB_2 nano reinforcement particles, thickness of nano composite layer formed on the Aluminum alloy substrate and fracture features. The depth of surface nano composite layer is measured as 3683.82 m m along the cross section of stir zone of nano composite perpendicular to FSP. It was observed that increase in volume percentage of TiB_2 particles, the microhardness is increased up to132 Hv and it is greater than as-received Al alloy's microhardness(104 Hv). It is also observed that at 4volume percentage higher tensile properties exhibited as compared with the 2 and 8 vol. %. It is found that high wear resistance exhibited at 4 volume percentage as-compared with the 2 and 8 vol. %. The observed wear and mechanical properties are interrelated with microstructure, fractography and worn morphology.展开更多
In order to choose the appropriate reference surface on the machined surface roughness of Si Cp/Al composites, the cutting experiments of Si Cp/Al composites were carried out, and the machined surface topography was m...In order to choose the appropriate reference surface on the machined surface roughness of Si Cp/Al composites, the cutting experiments of Si Cp/Al composites were carried out, and the machined surface topography was measured by OLS3000 Confocal laser scanning microscope. The 3D measured data of machined surface topography were analyzed by the area power spectrum density. The result shows that the texture of machined surface topography in milling of Si Cp/Al composites is almost isotropic. This is the reason that the values of Rq at different locations on the same machined surface are obviously different. Through the comparison of performance of different filtering methods, the robust least squares reference surface can be used to extract the surface roughness of SiC p/Al composites effectively.展开更多
High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Amon...High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.展开更多
文摘A surface Ti-WC composite was fabricated on CP-Ti by surface friction stirring(SFS)using a pinless WC-Cotool at a processing window of 800−2500 r/min and 8−50 mm/min.At 1600 r/min-50 mm/min,a defect-free compositelayer with an average hardness of~HV 1170 is formed.The hardness was increased by WC and TiN reinforcingparticles,dissolved Co atoms in Ti,and the formation of ultrafine grains.WC particles were incorporated into the Tisubstrate owing to the intense frictional interaction/heating at the tool-plate interface(~1000℃),which led to strengthloss and wear of the tool.The Williamson-Hall analysis of the XRD peaks of the SFSed sample confirmed a significantlysmall crystallite size(~100 nm).Wear tests showed that the wear resistance of the composite structure was about 4.5times higher than that of the CP-Ti.Friction analysis revealed a significant reduction in average value and fluctuations ofthe friction coefficient.
文摘The aim of present study is to analyze the influence of volume percentage(vol.%) of nano-sized particles(TiB_2: average size is 35 nm) on microstructure, mechanical and tribological behavior of 6061-T6 Al alloy surface nano composite prepared via Friction stir process(FSP). The microstructure of the fabricated surface nanocomposites is examined using optical microscopy(OM) and scanning electron microscope(SEM) for distribution of TiB_2 nano reinforcement particles, thickness of nano composite layer formed on the Aluminum alloy substrate and fracture features. The depth of surface nano composite layer is measured as 3683.82 m m along the cross section of stir zone of nano composite perpendicular to FSP. It was observed that increase in volume percentage of TiB_2 particles, the microhardness is increased up to132 Hv and it is greater than as-received Al alloy's microhardness(104 Hv). It is also observed that at 4volume percentage higher tensile properties exhibited as compared with the 2 and 8 vol. %. It is found that high wear resistance exhibited at 4 volume percentage as-compared with the 2 and 8 vol. %. The observed wear and mechanical properties are interrelated with microstructure, fractography and worn morphology.
基金Projects(51305284,61203208) supported by the National Natural Science Foundation of China
文摘In order to choose the appropriate reference surface on the machined surface roughness of Si Cp/Al composites, the cutting experiments of Si Cp/Al composites were carried out, and the machined surface topography was measured by OLS3000 Confocal laser scanning microscope. The 3D measured data of machined surface topography were analyzed by the area power spectrum density. The result shows that the texture of machined surface topography in milling of Si Cp/Al composites is almost isotropic. This is the reason that the values of Rq at different locations on the same machined surface are obviously different. Through the comparison of performance of different filtering methods, the robust least squares reference surface can be used to extract the surface roughness of SiC p/Al composites effectively.
基金Financial assistance from Armament research board,New Delhi,India
文摘High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.
