The influence of corrosion on the surface appearance and microstructure of particulate ZA27/SiCp composites was examined after 30 d immersion in a sodium chloride solution with the access of atmospheric oxygen. The co...The influence of corrosion on the surface appearance and microstructure of particulate ZA27/SiCp composites was examined after 30 d immersion in a sodium chloride solution with the access of atmospheric oxygen. The composites with different contents of SiC micro-particles were synthesized via compo casting. Microstructural studies by means of optical microscopy （OM） and scanning electron microscopy （SEM） showed that corrosion occurred in the composite matrices, preferentially in regions of the η phase, rich in zinc. The corrosion processes did not affect the silicon carbide particles incorporated in the matrix alloy. According to the results of electrochemical polarization measurements, an increase in the content of SiC particles in the composite matrice has led to the lower corrosion resistance in the composites.展开更多
The semi solid compressive deformation behaviors of two kinds of SiC p/ZA27 composites, one was modified by Zr and the other was not modified, were investigated. The results indicate that with increasing strain, the s...The semi solid compressive deformation behaviors of two kinds of SiC p/ZA27 composites, one was modified by Zr and the other was not modified, were investigated. The results indicate that with increasing strain, the stress of the modified composite first increases to a peak value, then dramatically decreases to a plateau value, and again increases at the final stage of deformation; but for the unmodified composite, after being up to a peak value, the stress decreases slowly at all times. As the deformation temperature or the heating time decreases, or the strain rate increases, the stress level(the peak and the plateau values) and the degree of cracking of the modified specimens all increase, and the specimen with uniform deformation and without cracks is obtained after being held at 470 ℃ for 30 min and deformed at the strain rate of 9.33×10 -3 s -1 . But the degree of cracking of the unmodified is just inverse to that of the modified. Under the same deformation conditions, the stress level and the degree of cracking of the unmodified composite are higher than those of the modified one, and the degree of cracking is very serious under any conditions. These phenomena were mainly discussed through analyzing the microstructures under different conditions and deformation mechanisms occurred at different deformation stages.展开更多
Solidification microstructure and mechanical property are explored.Furthermore,tensile fracture and microstructure are analyzed by using SEM and JXA 840A electron probe.The results indicate that SiC particles in SiC...Solidification microstructure and mechanical property are explored.Furthermore,tensile fracture and microstructure are analyzed by using SEM and JXA 840A electron probe.The results indicate that SiC particles in SiCp/ZA27 composite are mainly distributed on interfaces or between dendrites and surrounded by primary α phase.The dendrite of α phase is fined by SiCp.The tensile strength at room temperature decreases with the increasing of SiCp addition.The tensile strength at elevated temperature increases with the addition of SiCp.The fracture of SiCp/ZA27 composites is the mixture of tough and brittle fracture.The carck is prone to extend along the interface and the region of dispersed shrinkage.展开更多
The aging characteristics of as-quenched microstructures of ZA-27 alloy and SiCp/ZA-27 composite(ZMCp) were investigated using SEM, EDS and TEM. The structure, morphology and size of sub-grains in primary dendrite in ...The aging characteristics of as-quenched microstructures of ZA-27 alloy and SiCp/ZA-27 composite(ZMCp) were investigated using SEM, EDS and TEM. The structure, morphology and size of sub-grains in primary dendrite in ZMCp continuously change during aging process. Little tiny spherical Zn-rich η phase distributes in the dendrite. Amount of transitional α′phase, well coherent with equilibrium αf phase, in SiCp-neighboring dendrite edge zone is less than that in dendrite center zone. Both eutectic and peritectic β phase transform into lamellar α and η phases, obeying [ 2113]η∥[110]α, and (002)α∥ (1 101)η. In the like-eutecticum of ZMCp, less amount of β phase and decomposition products are found. The size of α phase decomposed from peritectic β phase in ZMCp is obviously larger than that in the monolithic alloy. The lamella decomposition of β phase beside SiCp is evidently more rapid than that in the alloy. SiC particulates strongly accelerate neighboring β phase decomposition in aging process.展开更多
In-situ TiB2 particles reinforced ZA27 composite was prepared by the stir-casting technique and a two-step method. TiB2/Al composite was produced by incorporating K2TiF6, KBF4 salts and other agents into Al melt. As a...In-situ TiB2 particles reinforced ZA27 composite was prepared by the stir-casting technique and a two-step method. TiB2/Al composite was produced by incorporating K2TiF6, KBF4 salts and other agents into Al melt. As a master alloy, TiB2/Al composite was used to manufacture TiB2/ZA27 composite, which results in the generation of well-distributed reinforcing TiB2 phase. The hardness, friction and wear behavior of TiB2/ZA27 composite were investigated. The results show that the hardness of the composite is enhanced with increasing the content of TiB2 particles, the incorporation of TiB2 reduces the wear rate of TiB2/ZA27 composite and improves the friction property under lubricated and dry sliding friction conditions. The worn track width of ZA27 alloy is 1.6 and 2.5 times as long as that of （2.1%）TiB2/ZA27 composite at 150N and 700N load under lubricated conditions, which indicates that TiB2/ZA27 composite possesses higher bearing ability.展开更多
基金The Ministry of Education, Science and Technological Development of the Republic of Serbia has supported financially this work through projects TR 35021 and OI 172005
文摘The influence of corrosion on the surface appearance and microstructure of particulate ZA27/SiCp composites was examined after 30 d immersion in a sodium chloride solution with the access of atmospheric oxygen. The composites with different contents of SiC micro-particles were synthesized via compo casting. Microstructural studies by means of optical microscopy （OM） and scanning electron microscopy （SEM） showed that corrosion occurred in the composite matrices, preferentially in regions of the η phase, rich in zinc. The corrosion processes did not affect the silicon carbide particles incorporated in the matrix alloy. According to the results of electrochemical polarization measurements, an increase in the content of SiC particles in the composite matrice has led to the lower corrosion resistance in the composites.
文摘The semi solid compressive deformation behaviors of two kinds of SiC p/ZA27 composites, one was modified by Zr and the other was not modified, were investigated. The results indicate that with increasing strain, the stress of the modified composite first increases to a peak value, then dramatically decreases to a plateau value, and again increases at the final stage of deformation; but for the unmodified composite, after being up to a peak value, the stress decreases slowly at all times. As the deformation temperature or the heating time decreases, or the strain rate increases, the stress level(the peak and the plateau values) and the degree of cracking of the modified specimens all increase, and the specimen with uniform deformation and without cracks is obtained after being held at 470 ℃ for 30 min and deformed at the strain rate of 9.33×10 -3 s -1 . But the degree of cracking of the unmodified is just inverse to that of the modified. Under the same deformation conditions, the stress level and the degree of cracking of the unmodified composite are higher than those of the modified one, and the degree of cracking is very serious under any conditions. These phenomena were mainly discussed through analyzing the microstructures under different conditions and deformation mechanisms occurred at different deformation stages.
文摘Solidification microstructure and mechanical property are explored.Furthermore,tensile fracture and microstructure are analyzed by using SEM and JXA 840A electron probe.The results indicate that SiC particles in SiCp/ZA27 composite are mainly distributed on interfaces or between dendrites and surrounded by primary α phase.The dendrite of α phase is fined by SiCp.The tensile strength at room temperature decreases with the increasing of SiCp addition.The tensile strength at elevated temperature increases with the addition of SiCp.The fracture of SiCp/ZA27 composites is the mixture of tough and brittle fracture.The carck is prone to extend along the interface and the region of dispersed shrinkage.
基金Project(03G52047) supported by the Aviation Science Foundation, China
文摘The aging characteristics of as-quenched microstructures of ZA-27 alloy and SiCp/ZA-27 composite(ZMCp) were investigated using SEM, EDS and TEM. The structure, morphology and size of sub-grains in primary dendrite in ZMCp continuously change during aging process. Little tiny spherical Zn-rich η phase distributes in the dendrite. Amount of transitional α′phase, well coherent with equilibrium αf phase, in SiCp-neighboring dendrite edge zone is less than that in dendrite center zone. Both eutectic and peritectic β phase transform into lamellar α and η phases, obeying [ 2113]η∥[110]α, and (002)α∥ (1 101)η. In the like-eutecticum of ZMCp, less amount of β phase and decomposition products are found. The size of α phase decomposed from peritectic β phase in ZMCp is obviously larger than that in the monolithic alloy. The lamella decomposition of β phase beside SiCp is evidently more rapid than that in the alloy. SiC particulates strongly accelerate neighboring β phase decomposition in aging process.
文摘In-situ TiB2 particles reinforced ZA27 composite was prepared by the stir-casting technique and a two-step method. TiB2/Al composite was produced by incorporating K2TiF6, KBF4 salts and other agents into Al melt. As a master alloy, TiB2/Al composite was used to manufacture TiB2/ZA27 composite, which results in the generation of well-distributed reinforcing TiB2 phase. The hardness, friction and wear behavior of TiB2/ZA27 composite were investigated. The results show that the hardness of the composite is enhanced with increasing the content of TiB2 particles, the incorporation of TiB2 reduces the wear rate of TiB2/ZA27 composite and improves the friction property under lubricated and dry sliding friction conditions. The worn track width of ZA27 alloy is 1.6 and 2.5 times as long as that of （2.1%）TiB2/ZA27 composite at 150N and 700N load under lubricated conditions, which indicates that TiB2/ZA27 composite possesses higher bearing ability.
