This study investigated the effects of adding graphene nanoplates(GNPs)and carbon nanotubes(CNTs)into the Al7075 matrix via the stir casting method on the microstructure and mechanical properties of the fabricated com...This study investigated the effects of adding graphene nanoplates(GNPs)and carbon nanotubes(CNTs)into the Al7075 matrix via the stir casting method on the microstructure and mechanical properties of the fabricated composites.By increasing the volume fraction of rein-forcements,the fraction of porosity increased.The X-ray diffraction results showed that the addition of reinforcements into the Al7075 changed the dominant crystal orientation from(002)to(111).Field emission scanning electron microscopy images also showed the distribution of clustered reinforcements in the matrix.Between the two reinforcements,the addition of CNTs generated a lower fraction of porosities.Through the addition of 0.52vol%GNPs into the matrix,the hardness,ultimate tensile strength and uniform elongation increased by 44%,32%,and 180%,respectively.Meanwhile,the presence of 0.71vol%CNTs in the matrix increased the hardness,tensile strength and uniform elongation by 108%,129%,and 260%,respectively.展开更多
The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispe...The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).The experimental consequences reveal that the optimal addition of Al_(2)O_(3p) was 2 wt%.After hot extrusion,the Mg(Zn,Cu,Al)2 phases partially dissolve into the matrix and generate many uniformly distributed aging precipitation particles,the Al_(7)Cu_(2)Fe phases are squeezed and broken,and the Al_(2)O_(3p) become uniform distribution.The microhardness of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites reaches HV 170.34,increased by 41.5%than as-cast composites.The wear rate of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites is further lower than that of as-cast composites under the same condition.SEM-EDS analyses reveal that the reinforced wear resistance of composites can put down to the protective effect of the Al_(2)O_(3p) reinforced transition layer.After hot extrusion,the transition layer becomes stable,which determines the reinforced wear resistance of the as-extruded composites.展开更多
Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and st...Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and strain rate range of 0.001?1 s?1. The results indicate that the true stress?true strain curve almost exhibits rapid flow softening phenomenon without an obvious work hardening, and the stress decreases with increasing temperature and decreasing strain rate. Moreover, the stress levels are higher at temperature below 400 °C but lower at 450 °C compared with the spray deposited 7075Al alloy. Superplastic deformation characteristics are found at temperature of 450 °C and strain rate range of 0.001?0.1 s?1 with corresponding strain rate sensitivity of 0.72. The optimum parameters of hot working are determined to be temperature of 430?450 °C and strain rate of 0.001?0.05 s?1 based on processing map and optical microstructural observation.展开更多
Al7075-Cu composite joints were prepared by the squeeze overcast process.The effects of melt temperature,die temperature,and squeeze pressure on hardness and ultimate tensile strength(UTS)of squeeze overcast Al7075-Cu...Al7075-Cu composite joints were prepared by the squeeze overcast process.The effects of melt temperature,die temperature,and squeeze pressure on hardness and ultimate tensile strength(UTS)of squeeze overcast Al7075-Cu composite joints were studied.The experimental results depict that squeeze pressure is the most significant process parameter affecting the hardness and UTS.The optimal values of UTS(48 MPa)and hardness(76 HRB)are achieved at a melt temperature of 800℃,a die temperature of 250℃,and a squeeze pressure of 90 MPa.Scanning electron microscopy(SEM)shows that fractured surfaces show flatfaced morphology at the optimal experimental condition.Energy-dispersive spectroscopy(EDS)analysis depicts that the atomic weight percentage of Zn decreases with an increase in melt temperature and squeeze pressure.The optimal mechanical properties of the Al7075-Cu overcast joint were achieved at the Al2Cu eutectic phase due to the large number of copper atoms that dispersed into the aluminum melt during the solidification process and the formation of strong intermetallic bonds.Gray relational analysis integrated with the Taguchi method was used to develop an optimal set of control variables for multi-response parametric optimization.Confirmatory tests were performed to validate the effectiveness of the employed technique.The manufacturing of squeeze overcast Al7075-Cu composite joints at optimal process parameters delivers a great indication to acknowledge a new method for foundry practitioners to manufacture materials with superior mechanical properties.展开更多
Aluminum-based metal matrix composites (MMCs) are considered in several technological applications owing to their enhanced mechanical properties when compared with monolithic metals. Research on the mechanical propert...Aluminum-based metal matrix composites (MMCs) are considered in several technological applications owing to their enhanced mechanical properties when compared with monolithic metals. Research on the mechanical properties MMCs was done by many researchers;however in depth study on the oxidation behavior of cenosphere, reinforced MMCs are required, since the application of Aluminum-based MMCs is extensively used in applications like automobile, navigation and aviation, where the demand on light weight corrosion resistance material is very much required. In the present work varied compositions of Al7075 grade Aluminum-cenosphere composites use liquid metallurgy route adopting stir casting approach. The experimental study was aimed at experimental investigations of developed composites under different corrosive environments. The corrosion tests were carried out as per ASTM standards. Salt spray test using NaCl was carried out as per ASTM B117 and immersion tests using NaCl and NaOH as corrodents were carried out by following ASTM G31 standards. The results obtained from the tests revealed that as increase in weight % of reinforcement, corrosion resistance increases up to 7.5% reinforcement, and further the corrosion resistance decreases marginally. Solution heat treated samples exhibited higher resistance to oxidation than cast samples in all corrosive environments. The SEM images show the presence of micro cracks and occurrence of pitting corrosion on the corrosion tested specimens.展开更多
Metal matrix composites （MMCs） as advanced materials, while producing the components with high dimensional accuracy and intricate shapes, are more complex and cost effective for machining than conventional alloys. I...Metal matrix composites （MMCs） as advanced materials, while producing the components with high dimensional accuracy and intricate shapes, are more complex and cost effective for machining than conventional alloys. It is due to the presence of discontinuously distributed hard ceramic with the MMCs and involvement of a large number of machining control variables. However, determination of optimal machining conditions helps the process engineer to make the process efficient and effec- tive. In the present investigation a novel hybrid multi-response optimization approach is proposed to derive the economic machining conditions for MMCs. This hybrid approach integrates the concepts of grey relational analysis （GRA）, principal component analysis （PCA） and Taguchi method （TM） to derive the optimal machining conditions. The machining experiments are planned to machine A17075/SiCp MMCs using wire-electrical discharge machining （WEDM） process. SiC particulate size and its weight percentage are explicitly considered here as the process variables along with the WEDM input variables. The derived optimal process responses are confirmed by the experimental validation tests and the results show satisfactory. The practical possibility of the derived optimal machining conditions is also analyzed and presented using scanning electron microscope （SEM） examinations. According to the growing industrial need of making high performance, low cost components, this investigation provides a simple and sequential approach to enhance the WEDM performance while machining MMCs.展开更多
Microstructure and mechanical behavior of high volume content SiCp/7xxxAl composites have not been explored yet. Therefore, in the present work, 45 vol.% SiCp/7075Al composite has been prepared by pres- sure infiltrat...Microstructure and mechanical behavior of high volume content SiCp/7xxxAl composites have not been explored yet. Therefore, in the present work, 45 vol.% SiCp/7075Al composite has been prepared by pres- sure infiltration method. High density dislocations were found around SiC/Al interface in SiCp/7075Al composite after water-quenching and aging treatment. Fine dispersed nano-η＇ phases were observed after the aging treatment. Adverse to other SiCp/Al composites prepared by the pressure infiltration method, an interface layer was observed between SiC particles and AI matrix. Furthermore, high-resolution trans- mission electron microscopy （HRTEM） observation indicated that this interface layer was coherent/semi- coherent with that of the SiC particles. 45 vol.% SiCp/7075Al composite demonstrated high tensile strength （630 MPa） and micro-ductility. Compared to aged SiCp/2024Al composite, the aged SiCp/7075Al com- posite showed an increase of about 200% in the tensile strain and 90% in the tensile strength, respectively. It is speculated that nano-η＇ phases in the Al matrix significantly contributed to the strengthening effect while the interface layer between SiC and AI matrix might be beneficial to the strength and plasticity of SiCp/7075Al composite.展开更多
文摘This study investigated the effects of adding graphene nanoplates(GNPs)and carbon nanotubes(CNTs)into the Al7075 matrix via the stir casting method on the microstructure and mechanical properties of the fabricated composites.By increasing the volume fraction of rein-forcements,the fraction of porosity increased.The X-ray diffraction results showed that the addition of reinforcements into the Al7075 changed the dominant crystal orientation from(002)to(111).Field emission scanning electron microscopy images also showed the distribution of clustered reinforcements in the matrix.Between the two reinforcements,the addition of CNTs generated a lower fraction of porosities.Through the addition of 0.52vol%GNPs into the matrix,the hardness,ultimate tensile strength and uniform elongation increased by 44%,32%,and 180%,respectively.Meanwhile,the presence of 0.71vol%CNTs in the matrix increased the hardness,tensile strength and uniform elongation by 108%,129%,and 260%,respectively.
基金Project(51965040)supported by the National Natural Science Foundation of ChinaProject(20181BAB206026)supported by the National Science Foundation of Jiangxi Province,China。
文摘The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).The experimental consequences reveal that the optimal addition of Al_(2)O_(3p) was 2 wt%.After hot extrusion,the Mg(Zn,Cu,Al)2 phases partially dissolve into the matrix and generate many uniformly distributed aging precipitation particles,the Al_(7)Cu_(2)Fe phases are squeezed and broken,and the Al_(2)O_(3p) become uniform distribution.The microhardness of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites reaches HV 170.34,increased by 41.5%than as-cast composites.The wear rate of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites is further lower than that of as-cast composites under the same condition.SEM-EDS analyses reveal that the reinforced wear resistance of composites can put down to the protective effect of the Al_(2)O_(3p) reinforced transition layer.After hot extrusion,the transition layer becomes stable,which determines the reinforced wear resistance of the as-extruded composites.
基金Project(51271076)supported by the National Natural Science Foundation of China
文摘Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and strain rate range of 0.001?1 s?1. The results indicate that the true stress?true strain curve almost exhibits rapid flow softening phenomenon without an obvious work hardening, and the stress decreases with increasing temperature and decreasing strain rate. Moreover, the stress levels are higher at temperature below 400 °C but lower at 450 °C compared with the spray deposited 7075Al alloy. Superplastic deformation characteristics are found at temperature of 450 °C and strain rate range of 0.001?0.1 s?1 with corresponding strain rate sensitivity of 0.72. The optimum parameters of hot working are determined to be temperature of 430?450 °C and strain rate of 0.001?0.05 s?1 based on processing map and optical microstructural observation.
文摘Al7075-Cu composite joints were prepared by the squeeze overcast process.The effects of melt temperature,die temperature,and squeeze pressure on hardness and ultimate tensile strength(UTS)of squeeze overcast Al7075-Cu composite joints were studied.The experimental results depict that squeeze pressure is the most significant process parameter affecting the hardness and UTS.The optimal values of UTS(48 MPa)and hardness(76 HRB)are achieved at a melt temperature of 800℃,a die temperature of 250℃,and a squeeze pressure of 90 MPa.Scanning electron microscopy(SEM)shows that fractured surfaces show flatfaced morphology at the optimal experimental condition.Energy-dispersive spectroscopy(EDS)analysis depicts that the atomic weight percentage of Zn decreases with an increase in melt temperature and squeeze pressure.The optimal mechanical properties of the Al7075-Cu overcast joint were achieved at the Al2Cu eutectic phase due to the large number of copper atoms that dispersed into the aluminum melt during the solidification process and the formation of strong intermetallic bonds.Gray relational analysis integrated with the Taguchi method was used to develop an optimal set of control variables for multi-response parametric optimization.Confirmatory tests were performed to validate the effectiveness of the employed technique.The manufacturing of squeeze overcast Al7075-Cu composite joints at optimal process parameters delivers a great indication to acknowledge a new method for foundry practitioners to manufacture materials with superior mechanical properties.
文摘Aluminum-based metal matrix composites (MMCs) are considered in several technological applications owing to their enhanced mechanical properties when compared with monolithic metals. Research on the mechanical properties MMCs was done by many researchers;however in depth study on the oxidation behavior of cenosphere, reinforced MMCs are required, since the application of Aluminum-based MMCs is extensively used in applications like automobile, navigation and aviation, where the demand on light weight corrosion resistance material is very much required. In the present work varied compositions of Al7075 grade Aluminum-cenosphere composites use liquid metallurgy route adopting stir casting approach. The experimental study was aimed at experimental investigations of developed composites under different corrosive environments. The corrosion tests were carried out as per ASTM standards. Salt spray test using NaCl was carried out as per ASTM B117 and immersion tests using NaCl and NaOH as corrodents were carried out by following ASTM G31 standards. The results obtained from the tests revealed that as increase in weight % of reinforcement, corrosion resistance increases up to 7.5% reinforcement, and further the corrosion resistance decreases marginally. Solution heat treated samples exhibited higher resistance to oxidation than cast samples in all corrosive environments. The SEM images show the presence of micro cracks and occurrence of pitting corrosion on the corrosion tested specimens.
文摘Metal matrix composites （MMCs） as advanced materials, while producing the components with high dimensional accuracy and intricate shapes, are more complex and cost effective for machining than conventional alloys. It is due to the presence of discontinuously distributed hard ceramic with the MMCs and involvement of a large number of machining control variables. However, determination of optimal machining conditions helps the process engineer to make the process efficient and effec- tive. In the present investigation a novel hybrid multi-response optimization approach is proposed to derive the economic machining conditions for MMCs. This hybrid approach integrates the concepts of grey relational analysis （GRA）, principal component analysis （PCA） and Taguchi method （TM） to derive the optimal machining conditions. The machining experiments are planned to machine A17075/SiCp MMCs using wire-electrical discharge machining （WEDM） process. SiC particulate size and its weight percentage are explicitly considered here as the process variables along with the WEDM input variables. The derived optimal process responses are confirmed by the experimental validation tests and the results show satisfactory. The practical possibility of the derived optimal machining conditions is also analyzed and presented using scanning electron microscope （SEM） examinations. According to the growing industrial need of making high performance, low cost components, this investigation provides a simple and sequential approach to enhance the WEDM performance while machining MMCs.
基金the financial support of the project from "Key Laboratory Fund (5780011513) of Harbin Institute of Technology""University Basic Fund (5710011113) of Harbin Institute of Technology""the Fundamental Research Funds for the Central Universities" (Grant No. HIT. NSRIF. 20161)
文摘Microstructure and mechanical behavior of high volume content SiCp/7xxxAl composites have not been explored yet. Therefore, in the present work, 45 vol.% SiCp/7075Al composite has been prepared by pres- sure infiltration method. High density dislocations were found around SiC/Al interface in SiCp/7075Al composite after water-quenching and aging treatment. Fine dispersed nano-η＇ phases were observed after the aging treatment. Adverse to other SiCp/Al composites prepared by the pressure infiltration method, an interface layer was observed between SiC particles and AI matrix. Furthermore, high-resolution trans- mission electron microscopy （HRTEM） observation indicated that this interface layer was coherent/semi- coherent with that of the SiC particles. 45 vol.% SiCp/7075Al composite demonstrated high tensile strength （630 MPa） and micro-ductility. Compared to aged SiCp/2024Al composite, the aged SiCp/7075Al com- posite showed an increase of about 200% in the tensile strain and 90% in the tensile strength, respectively. It is speculated that nano-η＇ phases in the Al matrix significantly contributed to the strengthening effect while the interface layer between SiC and AI matrix might be beneficial to the strength and plasticity of SiCp/7075Al composite.
基金Open Fund of National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology(EG202203331)Open Fund of State Key Laboratory of Advanced Welding and Joining(AWJ-23R03)+1 种基金Open Fund of Jiangxi Key Laboratory of Forming and Joining Technology for Aerospace Components(EL202203323)Start-up Fund of Nanchang Hangkong University(EA202203138)。
