Conventional mechanical machining of a composite material comprising an aluminum matrix reinforced with a high volume fraction of SiC particles(hereinafter referred to as an SiCp/Al composite)faces problems such as ra...Conventional mechanical machining of a composite material comprising an aluminum matrix reinforced with a high volume fraction of SiC particles(hereinafter referred to as an SiCp/Al composite)faces problems such as rapid tool wear,high specific cutting force,and poor surface integrity.Instead,a promising method for solving these problems is laser-induced oxidation-assisted milling(LOAM):under laser irradiation,the local workpiece material reacts with oxygen,thus forming loose and porous oxides that are easily removed.In the present work,the oxidation mechanism of SiCp/Al irradiated by a nanosecond pulsed laser is studied to better understand the laser-induced oxidation behavior and control the characteristics of the oxides,with laser irradiation experiments performed on a 65%SiCp/Al composite with various laser parameters and auxiliary gases(oxygen,nitrogen,and argon).With increasing laser pulse energy density,both the ablated groove depth and the width of the heat-affected zone increase.When oxygen is used as the auxiliary gas,an oxide layer composed of SiO_(2)and Al2O3 forms,and CO_(2)is produced and escapes from the material,thereby forming pores in the oxides.However,when nitrogen or argon is used as the auxiliary gas,a recast layer is produced that is relatively difficult to remove.Under laser irradiation,the sputtered material reacts with oxygen to form oxides on both sides of the ablated groove,and as the laser scanning path advances,the produced oxides accumulate to form an oxide layer.LOAM and conventional milling are compared using the same milling parameters,and LOAM is found to be better for reduced milling force and tool wear and improved machined surface quality.展开更多
Particle removal mechanism was presented during machining particle SiC/Al composites with diamond grinding tool. The relevant removal modes and their mechanisms were discussed considering the impact and squeezing effe...Particle removal mechanism was presented during machining particle SiC/Al composites with diamond grinding tool. The relevant removal modes and their mechanisms were discussed considering the impact and squeezing effect of diamond grit on the SiC particle. The experimental results show that the aluminum matrix has larger plastic deformation, so the aluminum mixed with the surplus SiC particles is cut from the surface. The SiC particles can be removed in multiple ways, such as broken/fractured, micro cracks, shearing and pulled out, etc. More particles removed by shearing, and less particles removed by fractured during material removal progress can produce a better machined surface.展开更多
A slight interfacial reaction in squeeze-cast SiCp/6061AI composites has been studied. It is found that this kind of reaction has a particular effect on the mechanical properties of the composites. The results of fie-...A slight interfacial reaction in squeeze-cast SiCp/6061AI composites has been studied. It is found that this kind of reaction has a particular effect on the mechanical properties of the composites. The results of fie-cure tests show that this reaction in the composites obviously increases the elastic properties, but is not beneficial to the fracture strength and ductility.This phenomenon can be interpreted in terms of two different micromechanisms which have been analyzed using TEM and HREM observations, acoustic emission (AE) technique and SEM fractography. In addition, a new method of SiC surface modification which can control the interface state is initially presented.展开更多
Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiCp. The crystalline phase, morphology, elements on the surface o...Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiCp. The crystalline phase, morphology, elements on the surface of SiCp and the interface between SiCp and Al were characterized by XRD, SEM, EDS and EPMA. The results show that it is favorable for the reaction between TiO2-C on the surface of SiCp and Al at the SiCp-Al interface at 1050℃. Besides, the process of Na3AlF6 melting, dissolving and then contacting with Al2O3 formed the NaF-AlF3-Al2O3 system, which generated OA1F^2-, promoting the dessolution of Al2O3 film on the surface of Al powde r. NasAlFe meets the needs of chemical reaction in TiO2-C-Al system at the SiCp- Al interface in the way of offering more molten Al. After 0.75 wt% Na3AlF6 was added into raw materials, the whole TiO2-C film and most SiO2 film were destroyed and the interfacial bonding between SiCp and Al was keeping good, in which no obvious void and crack were observed. Meanwhile, no brittle Al4C3 phase formed in the system. At this time, the flexure strength and density of samples presented optimal values, reaching up to 106.5 MPa and 90.77% respectively.展开更多
An attempt was made to investigate the machinability of Si Cp/Al composites based on the experimental study using mill-grinding processing method. The experiments were carried out on a high-speed CNC machining center ...An attempt was made to investigate the machinability of Si Cp/Al composites based on the experimental study using mill-grinding processing method. The experiments were carried out on a high-speed CNC machining center using integrated abrasive cutting tool. The effects of combined machining parameters, e g, cutting speed（vs）, feed rate（vf）, and depth of cut（ap）, with the same change of material removal rate（MRR） on the mill-grinding force and surface roughness（Ra） were investigated. The formation mechanism of typical machined surface defects was analyzed by SEM. The experimental results reveal that with the same change of material removal rate, lower mill-grinding force values can be gained by increasing depth of cut and feed rate simultaneously at higher cutting speed. With the same change of MRR value, lower surface roughness values can be gained by increasing the feed rate at higher cutting speed, rather than just increasing the depth of cut, or increasing the feed rate and depth of cut simultaneously. The machined surface of Si Cp/Al composites reveals typical defects which can influence surface integrity.展开更多
SiCp/ Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering （SPS）. and their thermophysical properties, such as thermal conductivity （TC） and co.lent of thermal e...SiCp/ Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering （SPS）. and their thermophysical properties, such as thermal conductivity （TC） and co.lent of thermal expansion （CTE）, were characterized. The electric field in the vacuum column was calculated and the generation condition of the spark was analyzed. Spark can be generated by a low current if the cavity in the green body is large enough. A high relative density of the composites was successfully achieved through the optimization of sintering parameters. The measured TCs of the SiCp/ Al composites fabricated by SPS are higher than 195 W/m ·K.展开更多
Mixed Al-Si and Al-Cu powders were investigated as insert layers to reactive diffusion bond SiCp/6063 metal matrix composite （MMC）. The results show that SiCp/6063 MMC joints bonded by the insert layers of the mixed...Mixed Al-Si and Al-Cu powders were investigated as insert layers to reactive diffusion bond SiCp/6063 metal matrix composite （MMC）. The results show that SiCp/6063 MMC joints bonded by the insert layers of the mixed Al-Si and Al-Cu powders have a dense joining layer of high quality. The mass transfer between the bonded materials and insert layers during bonding leads to the hypoeutectic microstructure of the joining layers bonded by both the mixed Al-Si and Al-Cu powders with eutectic composition. At fixed bonding time （temperature）, the shear strength of the joints by both insert layers of the mixed Al-Si and Al-Cu powders increases with increasing the bonding temperature （time）, but get maxima at bonding temperature 600℃ （time 90 min）.展开更多
Unidirectional Tungsten filament (W_f) reinforced pure Al,Al-6Ti-6Nb and SiC_p-Al-6Ti-6Nb matrix composites were prepared by hot-pressing in vacuum atmosphere,their microstructure and room temperature mechanical prope...Unidirectional Tungsten filament (W_f) reinforced pure Al,Al-6Ti-6Nb and SiC_p-Al-6Ti-6Nb matrix composites were prepared by hot-pressing in vacuum atmosphere,their microstructure and room temperature mechanical properties were investigated. It was indicated that no reaction products appeared at W_f/Al interfaces in pure Al matrix composites. While, in W_f/Al-6Ti-6Nb and W_f/SiCp-Al-6Ti-6Nb,intermetallic WAl_4 interfacial reaction products formed. Much better strengthening effect from W filament was shown in the W_f/Al-6Ti-6Nb and W_f/SiCp-Al-6Ti-6Nb composites than in the pure Al matrix composite. Their strength reached 319 and 339MPa, respectively, with only a small content of W_f(<5Vol.%). The excellent reinforcement effects could be predominantly attributed to the strong W_f/Al interfacial bonding strength due to the interfacial reaction.展开更多
SiCp/1060Al, SiCp/ZL101,SiCp/ZL102 composites with SiCp volume fraction of 55% were fabricated by pressureless infiltration. The microstructure was examined and thermal properties were characterized for SiCp/Al compos...SiCp/1060Al, SiCp/ZL101,SiCp/ZL102 composites with SiCp volume fraction of 55% were fabricated by pressureless infiltration. The microstructure was examined and thermal properties were characterized for SiCp/Al composites. The results show that the composites are dense and macroscopically homogeneous. With the increase of temperature, the mean linear coefficient of thermal expansion(CTE) at 25-200℃of the composites increases and ranges from 7.23×10-6 to 10.4×10-6K-1, but thermal conductivity declines gradually at the same time. With the increase of Si content in the Al matrix, CTE of the composites declines and thermal conductivity also declines but not linearly, when Si content is up to 7%, the average thermal conductivity is 140.4 W/(m·K), which is close to that of the SiCp/1060Al composite (144.6 W/(m·K)). While Si content is 11.7%, the average thermal conductivity declines markedly to 87.74 W/(m·K). The annealing treatment is better than the solution aging treatment in reducing CTE and improving thermal conductivity of the composites. Compared with conventional thermal management materials, SiCp/Al composites are potential candidate materials for advanced electronic packaging due to their tailorable thermo-physical properties.展开更多
Aluminium metal matrix composite is a relatively new material that has proved its position in automobile, aerospace and other engineering design applications due to its wear resistance and substantial hardness. Need f...Aluminium metal matrix composite is a relatively new material that has proved its position in automobile, aerospace and other engineering design applications due to its wear resistance and substantial hardness. Need for improved tribological performance has led to the design and selection of newer variants of the composite. The present investigation deals with the study of wear behaviour of Al-SiCp metal matrix composite for varying reinforcement content, applied load, sliding speed and time. Aluminium metal matrix composites reinforced with SiC particles are prepared by liquid metallurgy route using LM6 aluminium alloy and silicon carbide particles (size ~ 37 μm) by varying the weight fraction of SiC in the range of 5% - 10%. The material is synthesized by stir casting process in an electric melting furnace. The materials are then subjected to wear testing in a multitribotester using block on roller configuration. A plan of experiments based on L27 Taguchi orthogonal array is used to acquire the wear data in a controlled way. An analysis of variance is employed to investigate the influence of four controlling parameters, viz., SiC content, normal load, sliding speed and sliding time on dry sliding wear of the composites. It is observed that SiC content, sliding speed and normal load significantly affect the dry sliding wear. The optimal combination of the four controlling parameters is also obtained for minimum wear. The microstructure study of worn surfaces indicates nature of wear to be mostly abrasive.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.NT2021020)。
文摘Conventional mechanical machining of a composite material comprising an aluminum matrix reinforced with a high volume fraction of SiC particles(hereinafter referred to as an SiCp/Al composite)faces problems such as rapid tool wear,high specific cutting force,and poor surface integrity.Instead,a promising method for solving these problems is laser-induced oxidation-assisted milling(LOAM):under laser irradiation,the local workpiece material reacts with oxygen,thus forming loose and porous oxides that are easily removed.In the present work,the oxidation mechanism of SiCp/Al irradiated by a nanosecond pulsed laser is studied to better understand the laser-induced oxidation behavior and control the characteristics of the oxides,with laser irradiation experiments performed on a 65%SiCp/Al composite with various laser parameters and auxiliary gases(oxygen,nitrogen,and argon).With increasing laser pulse energy density,both the ablated groove depth and the width of the heat-affected zone increase.When oxygen is used as the auxiliary gas,an oxide layer composed of SiO_(2)and Al2O3 forms,and CO_(2)is produced and escapes from the material,thereby forming pores in the oxides.However,when nitrogen or argon is used as the auxiliary gas,a recast layer is produced that is relatively difficult to remove.Under laser irradiation,the sputtered material reacts with oxygen to form oxides on both sides of the ablated groove,and as the laser scanning path advances,the produced oxides accumulate to form an oxide layer.LOAM and conventional milling are compared using the same milling parameters,and LOAM is found to be better for reduced milling force and tool wear and improved machined surface quality.
基金Funded by the National Natural Science Foundation of China(51505434)the Key Scientific and Technological Project of Henan Province(172102210547)the Program for Innovative Research Team in Science and Technology in University of Henan Province(18IRTSTHN015)
文摘Particle removal mechanism was presented during machining particle SiC/Al composites with diamond grinding tool. The relevant removal modes and their mechanisms were discussed considering the impact and squeezing effect of diamond grit on the SiC particle. The experimental results show that the aluminum matrix has larger plastic deformation, so the aluminum mixed with the surplus SiC particles is cut from the surface. The SiC particles can be removed in multiple ways, such as broken/fractured, micro cracks, shearing and pulled out, etc. More particles removed by shearing, and less particles removed by fractured during material removal progress can produce a better machined surface.
文摘A slight interfacial reaction in squeeze-cast SiCp/6061AI composites has been studied. It is found that this kind of reaction has a particular effect on the mechanical properties of the composites. The results of fie-cure tests show that this reaction in the composites obviously increases the elastic properties, but is not beneficial to the fracture strength and ductility.This phenomenon can be interpreted in terms of two different micromechanisms which have been analyzed using TEM and HREM observations, acoustic emission (AE) technique and SEM fractography. In addition, a new method of SiC surface modification which can control the interface state is initially presented.
文摘Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiCp. The crystalline phase, morphology, elements on the surface of SiCp and the interface between SiCp and Al were characterized by XRD, SEM, EDS and EPMA. The results show that it is favorable for the reaction between TiO2-C on the surface of SiCp and Al at the SiCp-Al interface at 1050℃. Besides, the process of Na3AlF6 melting, dissolving and then contacting with Al2O3 formed the NaF-AlF3-Al2O3 system, which generated OA1F^2-, promoting the dessolution of Al2O3 film on the surface of Al powde r. NasAlFe meets the needs of chemical reaction in TiO2-C-Al system at the SiCp- Al interface in the way of offering more molten Al. After 0.75 wt% Na3AlF6 was added into raw materials, the whole TiO2-C film and most SiO2 film were destroyed and the interfacial bonding between SiCp and Al was keeping good, in which no obvious void and crack were observed. Meanwhile, no brittle Al4C3 phase formed in the system. At this time, the flexure strength and density of samples presented optimal values, reaching up to 106.5 MPa and 90.77% respectively.
基金Funded by the National Defense Basic Scientific ResearchAerospace Science and Technology Corporation Commonality Technology Research Project
文摘An attempt was made to investigate the machinability of Si Cp/Al composites based on the experimental study using mill-grinding processing method. The experiments were carried out on a high-speed CNC machining center using integrated abrasive cutting tool. The effects of combined machining parameters, e g, cutting speed（vs）, feed rate（vf）, and depth of cut（ap）, with the same change of material removal rate（MRR） on the mill-grinding force and surface roughness（Ra） were investigated. The formation mechanism of typical machined surface defects was analyzed by SEM. The experimental results reveal that with the same change of material removal rate, lower mill-grinding force values can be gained by increasing depth of cut and feed rate simultaneously at higher cutting speed. With the same change of MRR value, lower surface roughness values can be gained by increasing the feed rate at higher cutting speed, rather than just increasing the depth of cut, or increasing the feed rate and depth of cut simultaneously. The machined surface of Si Cp/Al composites reveals typical defects which can influence surface integrity.
基金Funded by the National Natural Science Foundation of China(No.50232020) and Fund of State Key Lab of Advanced Technologyfor Materials Synthesis and Processing ( WUT2004M04)
文摘SiCp/ Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering （SPS）. and their thermophysical properties, such as thermal conductivity （TC） and co.lent of thermal expansion （CTE）, were characterized. The electric field in the vacuum column was calculated and the generation condition of the spark was analyzed. Spark can be generated by a low current if the cavity in the green body is large enough. A high relative density of the composites was successfully achieved through the optimization of sintering parameters. The measured TCs of the SiCp/ Al composites fabricated by SPS are higher than 195 W/m ·K.
基金the National Natural Science Foundation of China under grant No.50175004
文摘Mixed Al-Si and Al-Cu powders were investigated as insert layers to reactive diffusion bond SiCp/6063 metal matrix composite （MMC）. The results show that SiCp/6063 MMC joints bonded by the insert layers of the mixed Al-Si and Al-Cu powders have a dense joining layer of high quality. The mass transfer between the bonded materials and insert layers during bonding leads to the hypoeutectic microstructure of the joining layers bonded by both the mixed Al-Si and Al-Cu powders with eutectic composition. At fixed bonding time （temperature）, the shear strength of the joints by both insert layers of the mixed Al-Si and Al-Cu powders increases with increasing the bonding temperature （time）, but get maxima at bonding temperature 600℃ （time 90 min）.
文摘Unidirectional Tungsten filament (W_f) reinforced pure Al,Al-6Ti-6Nb and SiC_p-Al-6Ti-6Nb matrix composites were prepared by hot-pressing in vacuum atmosphere,their microstructure and room temperature mechanical properties were investigated. It was indicated that no reaction products appeared at W_f/Al interfaces in pure Al matrix composites. While, in W_f/Al-6Ti-6Nb and W_f/SiCp-Al-6Ti-6Nb,intermetallic WAl_4 interfacial reaction products formed. Much better strengthening effect from W filament was shown in the W_f/Al-6Ti-6Nb and W_f/SiCp-Al-6Ti-6Nb composites than in the pure Al matrix composite. Their strength reached 319 and 339MPa, respectively, with only a small content of W_f(<5Vol.%). The excellent reinforcement effects could be predominantly attributed to the strong W_f/Al interfacial bonding strength due to the interfacial reaction.
基金Project(0450100) supported by the Natural Science Foundation of Jiangxi ProvinceProject(2006[167]) supported by the Ministry of Education in Jiangxi Province, China
文摘SiCp/1060Al, SiCp/ZL101,SiCp/ZL102 composites with SiCp volume fraction of 55% were fabricated by pressureless infiltration. The microstructure was examined and thermal properties were characterized for SiCp/Al composites. The results show that the composites are dense and macroscopically homogeneous. With the increase of temperature, the mean linear coefficient of thermal expansion(CTE) at 25-200℃of the composites increases and ranges from 7.23×10-6 to 10.4×10-6K-1, but thermal conductivity declines gradually at the same time. With the increase of Si content in the Al matrix, CTE of the composites declines and thermal conductivity also declines but not linearly, when Si content is up to 7%, the average thermal conductivity is 140.4 W/(m·K), which is close to that of the SiCp/1060Al composite (144.6 W/(m·K)). While Si content is 11.7%, the average thermal conductivity declines markedly to 87.74 W/(m·K). The annealing treatment is better than the solution aging treatment in reducing CTE and improving thermal conductivity of the composites. Compared with conventional thermal management materials, SiCp/Al composites are potential candidate materials for advanced electronic packaging due to their tailorable thermo-physical properties.
文摘Aluminium metal matrix composite is a relatively new material that has proved its position in automobile, aerospace and other engineering design applications due to its wear resistance and substantial hardness. Need for improved tribological performance has led to the design and selection of newer variants of the composite. The present investigation deals with the study of wear behaviour of Al-SiCp metal matrix composite for varying reinforcement content, applied load, sliding speed and time. Aluminium metal matrix composites reinforced with SiC particles are prepared by liquid metallurgy route using LM6 aluminium alloy and silicon carbide particles (size ~ 37 μm) by varying the weight fraction of SiC in the range of 5% - 10%. The material is synthesized by stir casting process in an electric melting furnace. The materials are then subjected to wear testing in a multitribotester using block on roller configuration. A plan of experiments based on L27 Taguchi orthogonal array is used to acquire the wear data in a controlled way. An analysis of variance is employed to investigate the influence of four controlling parameters, viz., SiC content, normal load, sliding speed and sliding time on dry sliding wear of the composites. It is observed that SiC content, sliding speed and normal load significantly affect the dry sliding wear. The optimal combination of the four controlling parameters is also obtained for minimum wear. The microstructure study of worn surfaces indicates nature of wear to be mostly abrasive.
