Dimensional stability properties of hot extruded 2024 Al alloy bar in T4 and T6 aging states and dif- ferent extruded directions were investigated by testing micro-yield strength (MYS), stress relaxation resistance (S...Dimensional stability properties of hot extruded 2024 Al alloy bar in T4 and T6 aging states and dif- ferent extruded directions were investigated by testing micro-yield strength (MYS), stress relaxation resistance (SRR), and dimensional change in thermal cycling and unloading conditions.The results show that micro-plastic deformation resistance in longitudinal(parallel to the axis of the extruded bar) direction is higher than that in transverse(perpendicular to the axis of the extruded bar) direction. Testing in short-term loading condition MYS value corresponding to micro-plastic strain of 1 *10m^(-5)in longitudinal direction is 1.4 times than that in transverse.Compared with the results of MYS and dimensional change in thermal cycling and unloading conditions, the values in T6 state are higher than that in T4 state. Using TEM the microstructures before micro-plastic deformation were observed.The analyses confirm that stability of thermodynamics condition and dislocation results in dimensional stability of the alloy.展开更多
The influence of R/v ratio on joint quality in 2024-T351 aluminum alloy was studied. Specimens were subjected to friction stir welding with the rotation rates of 750, 950 and 1180 r/min and welding speed between 73 an...The influence of R/v ratio on joint quality in 2024-T351 aluminum alloy was studied. Specimens were subjected to friction stir welding with the rotation rates of 750, 950 and 1180 r/min and welding speed between 73 and 190 mm/min, providing R/v ratio between 5.00 and 10.27. The welded joints were tested by means of both non-destructive （visual, penetrant and X-ray inspection） and destructive （metallographic, tension and hardness） testing. In all specimens typical zones are revealed, with corresponding differences in grain size. Tensile efficiency of the joints obtained is in the range of 52.2%to 82.3%. The results show that the best quality is obtained at R/v ratio of 8.06, 10.17 and 10.27. This behavior is attributed to the assumption that the material flows around the pin with an optimal speed, i.e. sufficient amount of material is available to fill the gap and prevent tunnel formation. R/v ratio also showed influence on hardness distribution, onion features and crack initiation/propagation zones.展开更多
Present work encapsulated the friction and wear behaviour of aluminium matrix composites reinforced with different mass fractions of titanium diboride(TiB_(2))particles,synthesized by stir casting.A pin on disc tribot...Present work encapsulated the friction and wear behaviour of aluminium matrix composites reinforced with different mass fractions of titanium diboride(TiB_(2))particles,synthesized by stir casting.A pin on disc tribotester was employed for conducting the dry sliding wear tests of Al2024−TiB_(2)composites.The tests were performed adopting various parameters like load,sliding distance and sliding velocity for investigating the effect of tribological parameters on the prepared composites.Microstructural characterization confirmed uniform dispersion of TiB_(2)particles and good matrix−reinforcement bonding.Results of the experiments revealed that,low friction and wear rates were observed in the developed composites compared to Al2024 alloy,whereas wear rates of both Al2024 alloy and fabricated composites increased with the increase in load,sliding velocity and sliding distance.However,friction coefficient of both Al2024 alloy and fabricated composites reduced with the increase in applied load but rose with the increase in sliding velocity and sliding distance.SEM studies of the worn surfaces and debris depicted that enhancement in wear resistance can be ascribed to finer debris formation.展开更多
To study the mechanism of formation and inhibition of Ce conversion films on Al 2024-T3 alloy, scanning microreference electrode technique (SMRE) is used to probe the potential map on Al 2024-T3 in CeCl 3 solution, t...To study the mechanism of formation and inhibition of Ce conversion films on Al 2024-T3 alloy, scanning microreference electrode technique (SMRE) is used to probe the potential map on Al 2024-T3 in CeCl 3 solution, the localized corrosion of Al alloy decreases with immersion time and disappears finally, which results from the competition of Cl - aggression and Ce 3+ inhibition on alloy surface. The results of X-ray photoelectron spectroscopy (XPS) indicate that the Ce conversion films consist of Al 2O 3, CeO 2 and Ce 2O 3(Ce(OH) 3), and CeO 2/Ce 2O 3 ratio decreases with the immersion time. When a critical pH for Ce(OH) 3 formation was reached, Ce(OH) 3 will precipitate on the micro cathodic area on alloy surface. Consequently, H 2O 2, the product of the catholic reaction will oxidize a part of Ce(OH) 3 to CeO 2, which appears a better corrosion resistance for Al alloys.展开更多
Thermal spray assisted transient liquid phase(TLP) bonding of Ti-6 Al-4 V to Al2024 alloys was investigated, where the interlayer was 80 μ m Babbitt thermal spray coat on Al substrate. Thermal spray creates a rough a...Thermal spray assisted transient liquid phase(TLP) bonding of Ti-6 Al-4 V to Al2024 alloys was investigated, where the interlayer was 80 μ m Babbitt thermal spray coat on Al substrate. Thermal spray creates a rough and clean surface which leads to establishing a joint with higher strength. The optimized parameters were bonding temperature of 580 ℃ and bonding time of 30 and 60 min. Microstructural observation together with XRD patterns confirmed the existence of Al2 Cu, Al2 Cu Mg, Cu3 Ti, Ti Al3, Ti Al and Mg2 Sn intermetallic compounds formed in Al weld side. On the other hand, Ti3 Al, Sn3 Ti5 and Ti3 Sn intermetallic compounds formed in Ti side. With increasing bonding time from 30 to 60 min, although the interlayer was not completely consumed, the thickness of remained Babbitt interlayer decreased to approximately 15 μ m. The study showed that shear strength of the joint reaches the high value of 57 MPa obtained at larger bonding time of 60 min.展开更多
The squeeze casting of a 2024 Al alloy was carried out to investigate the effect on microsegregation in the alloy of the application of pressure followed by diffusion annealing. The experimental results indicate that ...The squeeze casting of a 2024 Al alloy was carried out to investigate the effect on microsegregation in the alloy of the application of pressure followed by diffusion annealing. The experimental results indicate that an optimum applied pressure followed by an optimum diffusion annealing process can markedly reduce the degree of microsegregation and improve the mechanical properties to a degree that can approach the level of forged 2024 Al alloy.展开更多
AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn-Zn-Al filler metal. The microstructure, fracture morphologies, and mechanical properties of joint were inve...AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn-Zn-Al filler metal. The microstructure, fracture morphologies, and mechanical properties of joint were investigated. The results show that Mg-Al intermetallic compounds can be avoided by the process. But, a small quantity of porosity is found in the joint. The sheafing strength of joint interface adjacent to magnesium alloy is 35.4 MPa for formation of Mg-Sn intermetallic compounds, which is about 46 % of that of filler metal. While, the shearing strength of joint interfaces adjacent to aluminum alloy is 70.4 MPa for formation of Zn-Sn-Al solid solution, which is about 92 % of that of filler metal.展开更多
The instrumented nanoindentation technique has been widely used to measure the tensile properties of various materials,for its simple specimen preparation and nearly nondestructive testing processes.In this paper,a no...The instrumented nanoindentation technique has been widely used to measure the tensile properties of various materials,for its simple specimen preparation and nearly nondestructive testing processes.In this paper,a novel inverse method is established for measuring the elastoplastic properties of Al 2024 alloy.The grid indentation experiments are performed on Al 2024 material.The obtained experimental load–displacement(P–h)data exhibit obvious scatter characteristics.The artificial neural network(ANN)model with tunable hyper-parameters is adopted to establish the forward relationship between elastoplastic parameters and indentation load–displacement snapshot.An objective function for quantifying the error norm between predicted and experimental P–h snapshots is established.The parameter identification problem is solved using the“interior-point”constraint optimization algorithm..The identified material properties show good agreement with the tensile data,and the error values are−8.66%for elastic modulus,1.08%for yield stress,and 6.90%for hardening exponent.The sensitivity of numerical results to experimental uncertainty is analyzed,and the error bound of experimental data is determined.The results of sensitivity analysis indicate that the proposed inverse method in the work is very effective and reliable.展开更多
In this paper, 2024 Al alloy and AZ31B Mg alloy were brazed with aid of stirring without flux in air. The effects of the brazing temperature on microstructure and shear strength of the joint were investigated. The dif...In this paper, 2024 Al alloy and AZ31B Mg alloy were brazed with aid of stirring without flux in air. The effects of the brazing temperature on microstructure and shear strength of the joint were investigated. The diffusion zone is found at joint interface near Al base metal, which consists of Al-Zn-Sn solid solution. At the same time, continuous intermetallic compounds （IMCs） phase and broken ones are found at joint interface near Mg base metal, which mainly consists of the Mg2Sn phase. With the increase of the brazing temperature, the shear strength at the joint interface near A1 base metal rises gradually. On the contrary, that of the joint interface near Mg base metal obviously decreases.展开更多
文摘Dimensional stability properties of hot extruded 2024 Al alloy bar in T4 and T6 aging states and dif- ferent extruded directions were investigated by testing micro-yield strength (MYS), stress relaxation resistance (SRR), and dimensional change in thermal cycling and unloading conditions.The results show that micro-plastic deformation resistance in longitudinal(parallel to the axis of the extruded bar) direction is higher than that in transverse(perpendicular to the axis of the extruded bar) direction. Testing in short-term loading condition MYS value corresponding to micro-plastic strain of 1 *10m^(-5)in longitudinal direction is 1.4 times than that in transverse.Compared with the results of MYS and dimensional change in thermal cycling and unloading conditions, the values in T6 state are higher than that in T4 state. Using TEM the microstructures before micro-plastic deformation were observed.The analyses confirm that stability of thermodynamics condition and dislocation results in dimensional stability of the alloy.
基金Ministry of Education and Science of Serbia for financial support through Project TR34018
文摘The influence of R/v ratio on joint quality in 2024-T351 aluminum alloy was studied. Specimens were subjected to friction stir welding with the rotation rates of 750, 950 and 1180 r/min and welding speed between 73 and 190 mm/min, providing R/v ratio between 5.00 and 10.27. The welded joints were tested by means of both non-destructive （visual, penetrant and X-ray inspection） and destructive （metallographic, tension and hardness） testing. In all specimens typical zones are revealed, with corresponding differences in grain size. Tensile efficiency of the joints obtained is in the range of 52.2%to 82.3%. The results show that the best quality is obtained at R/v ratio of 8.06, 10.17 and 10.27. This behavior is attributed to the assumption that the material flows around the pin with an optimal speed, i.e. sufficient amount of material is available to fill the gap and prevent tunnel formation. R/v ratio also showed influence on hardness distribution, onion features and crack initiation/propagation zones.
文摘Present work encapsulated the friction and wear behaviour of aluminium matrix composites reinforced with different mass fractions of titanium diboride(TiB_(2))particles,synthesized by stir casting.A pin on disc tribotester was employed for conducting the dry sliding wear tests of Al2024−TiB_(2)composites.The tests were performed adopting various parameters like load,sliding distance and sliding velocity for investigating the effect of tribological parameters on the prepared composites.Microstructural characterization confirmed uniform dispersion of TiB_(2)particles and good matrix−reinforcement bonding.Results of the experiments revealed that,low friction and wear rates were observed in the developed composites compared to Al2024 alloy,whereas wear rates of both Al2024 alloy and fabricated composites increased with the increase in load,sliding velocity and sliding distance.However,friction coefficient of both Al2024 alloy and fabricated composites reduced with the increase in applied load but rose with the increase in sliding velocity and sliding distance.SEM studies of the worn surfaces and debris depicted that enhancement in wear resistance can be ascribed to finer debris formation.
文摘To study the mechanism of formation and inhibition of Ce conversion films on Al 2024-T3 alloy, scanning microreference electrode technique (SMRE) is used to probe the potential map on Al 2024-T3 in CeCl 3 solution, the localized corrosion of Al alloy decreases with immersion time and disappears finally, which results from the competition of Cl - aggression and Ce 3+ inhibition on alloy surface. The results of X-ray photoelectron spectroscopy (XPS) indicate that the Ce conversion films consist of Al 2O 3, CeO 2 and Ce 2O 3(Ce(OH) 3), and CeO 2/Ce 2O 3 ratio decreases with the immersion time. When a critical pH for Ce(OH) 3 formation was reached, Ce(OH) 3 will precipitate on the micro cathodic area on alloy surface. Consequently, H 2O 2, the product of the catholic reaction will oxidize a part of Ce(OH) 3 to CeO 2, which appears a better corrosion resistance for Al alloys.
文摘Thermal spray assisted transient liquid phase(TLP) bonding of Ti-6 Al-4 V to Al2024 alloys was investigated, where the interlayer was 80 μ m Babbitt thermal spray coat on Al substrate. Thermal spray creates a rough and clean surface which leads to establishing a joint with higher strength. The optimized parameters were bonding temperature of 580 ℃ and bonding time of 30 and 60 min. Microstructural observation together with XRD patterns confirmed the existence of Al2 Cu, Al2 Cu Mg, Cu3 Ti, Ti Al3, Ti Al and Mg2 Sn intermetallic compounds formed in Al weld side. On the other hand, Ti3 Al, Sn3 Ti5 and Ti3 Sn intermetallic compounds formed in Ti side. With increasing bonding time from 30 to 60 min, although the interlayer was not completely consumed, the thickness of remained Babbitt interlayer decreased to approximately 15 μ m. The study showed that shear strength of the joint reaches the high value of 57 MPa obtained at larger bonding time of 60 min.
文摘The squeeze casting of a 2024 Al alloy was carried out to investigate the effect on microsegregation in the alloy of the application of pressure followed by diffusion annealing. The experimental results indicate that an optimum applied pressure followed by an optimum diffusion annealing process can markedly reduce the degree of microsegregation and improve the mechanical properties to a degree that can approach the level of forged 2024 Al alloy.
基金supported by the Natural Science Foundation Project of Chongqing (No. cstc2011jjA50001)the State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology (No. AWPTM12-07)
文摘AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn-Zn-Al filler metal. The microstructure, fracture morphologies, and mechanical properties of joint were investigated. The results show that Mg-Al intermetallic compounds can be avoided by the process. But, a small quantity of porosity is found in the joint. The sheafing strength of joint interface adjacent to magnesium alloy is 35.4 MPa for formation of Mg-Sn intermetallic compounds, which is about 46 % of that of filler metal. While, the shearing strength of joint interfaces adjacent to aluminum alloy is 70.4 MPa for formation of Zn-Sn-Al solid solution, which is about 92 % of that of filler metal.
基金supported by the National Natural Science Foundation of China(No.52005378)the Opening project fund of Materials Service Safety Assessment Facilities(No.MSAF-2021-107)the Fundamental Research Funds for the Central Universities(ZYTS23018).
文摘The instrumented nanoindentation technique has been widely used to measure the tensile properties of various materials,for its simple specimen preparation and nearly nondestructive testing processes.In this paper,a novel inverse method is established for measuring the elastoplastic properties of Al 2024 alloy.The grid indentation experiments are performed on Al 2024 material.The obtained experimental load–displacement(P–h)data exhibit obvious scatter characteristics.The artificial neural network(ANN)model with tunable hyper-parameters is adopted to establish the forward relationship between elastoplastic parameters and indentation load–displacement snapshot.An objective function for quantifying the error norm between predicted and experimental P–h snapshots is established.The parameter identification problem is solved using the“interior-point”constraint optimization algorithm..The identified material properties show good agreement with the tensile data,and the error values are−8.66%for elastic modulus,1.08%for yield stress,and 6.90%for hardening exponent.The sensitivity of numerical results to experimental uncertainty is analyzed,and the error bound of experimental data is determined.The results of sensitivity analysis indicate that the proposed inverse method in the work is very effective and reliable.
基金financially supported by the Natural Science Foundation Project of Chongqing Science and Technology Commission(No.cstc2011jj A50001)
文摘In this paper, 2024 Al alloy and AZ31B Mg alloy were brazed with aid of stirring without flux in air. The effects of the brazing temperature on microstructure and shear strength of the joint were investigated. The diffusion zone is found at joint interface near Al base metal, which consists of Al-Zn-Sn solid solution. At the same time, continuous intermetallic compounds （IMCs） phase and broken ones are found at joint interface near Mg base metal, which mainly consists of the Mg2Sn phase. With the increase of the brazing temperature, the shear strength at the joint interface near A1 base metal rises gradually. On the contrary, that of the joint interface near Mg base metal obviously decreases.
