Transmission electron microscopy(TEM),scanning electron microscopy(SEM),hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu...Transmission electron microscopy(TEM),scanning electron microscopy(SEM),hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy.The results show that the alloy exhibits splendid mechanical properties with an ultimate tensile strength of504MPa and an elongation of10.1%after aging at170°C for16h.With tensile testing temperature increasing to150°C,the strength of the alloy declines slightly to483MPa.Then,the strength drops quickly when temperature reaches over200°C.The high strength of the alloy in peak-aged condition is caused by a considerable amount ofθ'and AlMgSiCu(Q)precipitates.The relatively stable mechanical properties tested below150°C are mainly ascribed to the stability ofθ'precipitates.The growth ofθ'and Q precipitates and the generation ofθphase lead to a rapid drop of the strength when temperature is over150°C.展开更多
Finite element analysis has been carried out to understand the effect of various processing routes and condition on the microscale deformation behavior of Al–4.5 Cu–2 Mg alloy. The alloy has been developed through f...Finite element analysis has been carried out to understand the effect of various processing routes and condition on the microscale deformation behavior of Al–4.5 Cu–2 Mg alloy. The alloy has been developed through four different routes and condition, i.e. conventional gravity casting with and without refiner, rheocasting and SIMA process. The optical microstructures of the alloy have been used to develop representative volume elements（RVEs）. Two different boundary conditions have been employed to simulate the deformation behavior of the alloy under uniaxial loading. Finally, the simulated stress-strain behavior of the alloy is compared with the experimental result. It is found that the microstructural morphology has a significant impact on stress and strain distribution and load carrying capacity. The eutectic phase always carries a higher load than the α（Al） phase. The globular α（Al） grains with thinner and uniformly distributed eutectic network provide a better stress and strain distribution. Owing to this, SIMA processed alloy has better stress and strain distribution than other processes. Finally, the simulated yield strength of the alloy is verified by experiment and they have great agreement.展开更多
The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and...The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.展开更多
Direct reaction synthesis (DRS), based on the principle of self-propagating high-temperature synthesis (SHS), is a new method for preparing participate metal matrix composites. TiCP/AI-4.5Cu-0.8Mg composites were fabr...Direct reaction synthesis (DRS), based on the principle of self-propagating high-temperature synthesis (SHS), is a new method for preparing participate metal matrix composites. TiCP/AI-4.5Cu-0.8Mg composites were fabricated by DRS. Participate composites were fabricated with Ti carbide (TiC) particles, generally less than 1.0μm. The reacted, thermal extruded samples exhibit a homogeneous distribution of fine TiC particles in AI-4.5Cu-0.8Mg matrix. Mechanical property evaluation of the composites has revealed a very high tensile strength relative to the matrix alloy. Fractographic analysis indicates ductile failure.展开更多
The influence of Li addition on mechanical property and aging precipitation behavior of Al-3.5Cu-1.5Mg alloy was investigated by tensile test,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）...The influence of Li addition on mechanical property and aging precipitation behavior of Al-3.5Cu-1.5Mg alloy was investigated by tensile test,scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and high resolution transmission electron microscopy（HRTEM）.The results show that the tensile strength can be significantly improved with the slightly decreased ductility and the form of fracture morphology is converted from ductile fracture into ductile/britde mixed fracture by adding 1.0%Li.Besides,the peak aging time at 185 ℃ is delayed from 12 to 24 h and the main precipitation phase S（Al2CuMg） is converted into S＇（Al2CuMg）＋δ（Al3Li）,while the formation of S＇（Al2CuMg） is delayed.展开更多
Al-4. 5Cu-5Pb alloy was prepared by sand and chill casting. The same alloy was also spray deposited at a gas pressure of 1.6 MPa. The microstructural features exhibit a coarse to fine dendritic morphology for sand ...Al-4. 5Cu-5Pb alloy was prepared by sand and chill casting. The same alloy was also spray deposited at a gas pressure of 1.6 MPa. The microstructural features exhibit a coarse to fine dendritic morphology for sand and chill cast alloys. Equiaxed grains were observed for spray formed alloys. Wear testing employing a pin-on-disc type set-up, reveals considerably lower wear of spray deposited alloy compared to that of chill and sand cast alloys. The morphological features of wear track on specimen and debris indicated a mixed oxidative-cum-adhesive wear mechanisms for these alloys tested in the present investigation. (Edited author abstract) 36 Refs.展开更多
The objective of the current study was to investigate the use of ultrasonic melt treatment technology in the production of grain-refined billets of the AC7 A alloy, which was intended for subsequent use as a feedstock...The objective of the current study was to investigate the use of ultrasonic melt treatment technology in the production of grain-refined billets of the AC7 A alloy, which was intended for subsequent use as a feedstock in forming operations. The experiments included the application of ultrasonic vibrations to the molten alloys via direct and indirect techniques. Several process parameters such as pouring temperatures(several temperatures between 740 and 660℃), and treatment time(from 12 min down to 2 min) were investigated. The experiment included continuous ultrasonic treatment from the liquid to the semisolid states. The results showed that both treatment techniques were viable for producing billets with the desirable microstructural characteristics. The optimum treatment conditions were the short treatment time(2 to 3 min), from about 660℃ down to 615℃ for the indirect treatment technique, and from 660℃ to 635℃ for the direct treatment technique. The resulting microstructures, at three positions along the height of the ingot, were characterized by fine, non-dendritic α(Al) grains in the order of a hundred microns, as compared to few thousands of microns for the conventional cast ingots. The intermetallic particles were also refined in size and modified in morphology by the ultrasonic treatment. The operating mechanisms by which the ultrasonic vibrations altered the ingot microstructures were discussed and analyzed.展开更多
The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al–13Si–7.5Cu–1Mg alloy were investigated.The microstructures of alloys be...The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al–13Si–7.5Cu–1Mg alloy were investigated.The microstructures of alloys before and after conform processing and aging were compared by transmission electron microscopy and scanning electron microscopy,respectively.The results reveal that the primary phases were broken and refined by intense shear deformation during conform processing.After the conform-prepared Al–13Si–7.5Cu–1Mg alloy was subjected to solid-solution treatment at 494℃for 1.5 h and aging at 180℃for 4 h,its hardness improved from HBS 115.8 to HBS 152.5 and its ultimate tensile strength increased from 112.6 to 486.8 MPa.Its wear resistance was also enhanced.The factors leading to the enhanced strength,hardness,and wear resistance of the alloy were discussed in detail.展开更多
Cu-14Al-4.5Fe bronze powders with and without 0.6% Ce were prepared and their coatings were fabricated on 45# carbon steel substrate by atmospheric plasma spraying. The effects of rare earth Ce on the coating interfac...Cu-14Al-4.5Fe bronze powders with and without 0.6% Ce were prepared and their coatings were fabricated on 45# carbon steel substrate by atmospheric plasma spraying. The effects of rare earth Ce on the coating interface bonding strength, coatings and bonding interface vertical sections microstructure were investigated by tensile machine, X-ray diffraction analysis, scanning electron microscopy （SEM） and electronic probe microanalysis （EPMA）. The results showed that the shape of powders was more spherical like, and the coating’s hardness and interface bonging tensile strength would be improved to 8.9% and 17.4%, respectively, higher than that of the Cu-14Al-4.5Fe coating without 0.6% Ce added. The refined of κ phases, well distributed matrix phases in coatings and the promotion of Fe, Al elements diffusion led to the improvement in interface bonding strength and hardness of the Cu-14Al-4.5Fe coating with addition of 0.6% Ce, which hardened and strengthened the coating.展开更多
基金Project(51301209)supported by the National Natural Science Foundation of China
文摘Transmission electron microscopy(TEM),scanning electron microscopy(SEM),hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy.The results show that the alloy exhibits splendid mechanical properties with an ultimate tensile strength of504MPa and an elongation of10.1%after aging at170°C for16h.With tensile testing temperature increasing to150°C,the strength of the alloy declines slightly to483MPa.Then,the strength drops quickly when temperature reaches over200°C.The high strength of the alloy in peak-aged condition is caused by a considerable amount ofθ'and AlMgSiCu(Q)precipitates.The relatively stable mechanical properties tested below150°C are mainly ascribed to the stability ofθ'precipitates.The growth ofθ'and Q precipitates and the generation ofθphase lead to a rapid drop of the strength when temperature is over150°C.
文摘Finite element analysis has been carried out to understand the effect of various processing routes and condition on the microscale deformation behavior of Al–4.5 Cu–2 Mg alloy. The alloy has been developed through four different routes and condition, i.e. conventional gravity casting with and without refiner, rheocasting and SIMA process. The optical microstructures of the alloy have been used to develop representative volume elements（RVEs）. Two different boundary conditions have been employed to simulate the deformation behavior of the alloy under uniaxial loading. Finally, the simulated stress-strain behavior of the alloy is compared with the experimental result. It is found that the microstructural morphology has a significant impact on stress and strain distribution and load carrying capacity. The eutectic phase always carries a higher load than the α（Al） phase. The globular α（Al） grains with thinner and uniformly distributed eutectic network provide a better stress and strain distribution. Owing to this, SIMA processed alloy has better stress and strain distribution than other processes. Finally, the simulated yield strength of the alloy is verified by experiment and they have great agreement.
基金Project(51274245) supported by the National Natural Science Foundation of China
文摘The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.
文摘Direct reaction synthesis (DRS), based on the principle of self-propagating high-temperature synthesis (SHS), is a new method for preparing participate metal matrix composites. TiCP/AI-4.5Cu-0.8Mg composites were fabricated by DRS. Participate composites were fabricated with Ti carbide (TiC) particles, generally less than 1.0μm. The reacted, thermal extruded samples exhibit a homogeneous distribution of fine TiC particles in AI-4.5Cu-0.8Mg matrix. Mechanical property evaluation of the composites has revealed a very high tensile strength relative to the matrix alloy. Fractographic analysis indicates ductile failure.
基金Projects (2010CB731700,2012CB619500) supported by the National Basic Research Program of China
文摘The influence of Li addition on mechanical property and aging precipitation behavior of Al-3.5Cu-1.5Mg alloy was investigated by tensile test,scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and high resolution transmission electron microscopy（HRTEM）.The results show that the tensile strength can be significantly improved with the slightly decreased ductility and the form of fracture morphology is converted from ductile fracture into ductile/britde mixed fracture by adding 1.0%Li.Besides,the peak aging time at 185 ℃ is delayed from 12 to 24 h and the main precipitation phase S（Al2CuMg） is converted into S＇（Al2CuMg）＋δ（Al3Li）,while the formation of S＇（Al2CuMg） is delayed.
文摘Al-4. 5Cu-5Pb alloy was prepared by sand and chill casting. The same alloy was also spray deposited at a gas pressure of 1.6 MPa. The microstructural features exhibit a coarse to fine dendritic morphology for sand and chill cast alloys. Equiaxed grains were observed for spray formed alloys. Wear testing employing a pin-on-disc type set-up, reveals considerably lower wear of spray deposited alloy compared to that of chill and sand cast alloys. The morphological features of wear track on specimen and debris indicated a mixed oxidative-cum-adhesive wear mechanisms for these alloys tested in the present investigation. (Edited author abstract) 36 Refs.
文摘The objective of the current study was to investigate the use of ultrasonic melt treatment technology in the production of grain-refined billets of the AC7 A alloy, which was intended for subsequent use as a feedstock in forming operations. The experiments included the application of ultrasonic vibrations to the molten alloys via direct and indirect techniques. Several process parameters such as pouring temperatures(several temperatures between 740 and 660℃), and treatment time(from 12 min down to 2 min) were investigated. The experiment included continuous ultrasonic treatment from the liquid to the semisolid states. The results showed that both treatment techniques were viable for producing billets with the desirable microstructural characteristics. The optimum treatment conditions were the short treatment time(2 to 3 min), from about 660℃ down to 615℃ for the indirect treatment technique, and from 660℃ to 635℃ for the direct treatment technique. The resulting microstructures, at three positions along the height of the ingot, were characterized by fine, non-dendritic α(Al) grains in the order of a hundred microns, as compared to few thousands of microns for the conventional cast ingots. The intermetallic particles were also refined in size and modified in morphology by the ultrasonic treatment. The operating mechanisms by which the ultrasonic vibrations altered the ingot microstructures were discussed and analyzed.
基金financially supported by the National Natural Science Foundation of China (No.51274245)
文摘The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al–13Si–7.5Cu–1Mg alloy were investigated.The microstructures of alloys before and after conform processing and aging were compared by transmission electron microscopy and scanning electron microscopy,respectively.The results reveal that the primary phases were broken and refined by intense shear deformation during conform processing.After the conform-prepared Al–13Si–7.5Cu–1Mg alloy was subjected to solid-solution treatment at 494℃for 1.5 h and aging at 180℃for 4 h,its hardness improved from HBS 115.8 to HBS 152.5 and its ultimate tensile strength increased from 112.6 to 486.8 MPa.Its wear resistance was also enhanced.The factors leading to the enhanced strength,hardness,and wear resistance of the alloy were discussed in detail.
基金supported by the National Natural Science Foundation of China (50804019)
文摘Cu-14Al-4.5Fe bronze powders with and without 0.6% Ce were prepared and their coatings were fabricated on 45# carbon steel substrate by atmospheric plasma spraying. The effects of rare earth Ce on the coating interface bonding strength, coatings and bonding interface vertical sections microstructure were investigated by tensile machine, X-ray diffraction analysis, scanning electron microscopy （SEM） and electronic probe microanalysis （EPMA）. The results showed that the shape of powders was more spherical like, and the coating’s hardness and interface bonging tensile strength would be improved to 8.9% and 17.4%, respectively, higher than that of the Cu-14Al-4.5Fe coating without 0.6% Ce added. The refined of κ phases, well distributed matrix phases in coatings and the promotion of Fe, Al elements diffusion led to the improvement in interface bonding strength and hardness of the Cu-14Al-4.5Fe coating with addition of 0.6% Ce, which hardened and strengthened the coating.
