Aluminum-10% TiB master alloy was added in various proportions in 7178 Al alloy in order to examine the effect of TiB on grain refinement, wear and compressive deformation of the later one. Microstructural characteriz...Aluminum-10% TiB master alloy was added in various proportions in 7178 Al alloy in order to examine the effect of TiB on grain refinement, wear and compressive deformation of the later one. Microstructural characterization reveals that TiB particles act as grain refiners for primary base alloy and result in globular dendrites. It was observed that the wear resistance and strength of the alloy decreased when the master alloy addition increased beyond 20%, even though the dendrites become much finer and almost spherical in nature.展开更多
The AA6061-10 wt.%B4 C mono composite, AA6061-10 wt.%B4 C-Gr(Gr: graphite) hybrid composites containing 2.5, 5, and 7.5 wt.% Gr particles, and AA6061-10 wt.%B4 C-Mo S2 hybrid composites containing 2.5, 5, and 7.5 wt.%...The AA6061-10 wt.%B4 C mono composite, AA6061-10 wt.%B4 C-Gr(Gr: graphite) hybrid composites containing 2.5, 5, and 7.5 wt.% Gr particles, and AA6061-10 wt.%B4 C-Mo S2 hybrid composites containing 2.5, 5, and 7.5 wt.% Mo S2 particles were fabricated through stir casting. The dry sliding tribological behaviors of the mono composite and hybrid composites were studied as a function of temperature on high temperature pin-on-disc tribotester against EN 31 counterface. The wear rate and friction coefficient of the Gr-reinforced and Mo S2-reinforced hybrid composites decreased in the temperature range of 30-100 ℃ due to the combined lubrication offered by the wear protective layer and its solid lubricant phase. Scanning electron microscopy(SEM) observation of the worn pin surface revealed severe adhesion, delamination, and abrasion wear mechanisms at temperatures of 150, 200, and 250 ℃, respectively. At 150 ℃, transmission electron microscopy(TEM) observation of the hybrid composites revealed the formation of deformation bands due to severe plastic deformation and fine crystalline structure due to dynamic recrystallization.展开更多
Multistage superimposed deformation has been discussed systematically based on the progress of the stratigraphic sequences of the northeastern margin of Yangtze Block.The new-discovered first stage deformation of thos...Multistage superimposed deformation has been discussed systematically based on the progress of the stratigraphic sequences of the northeastern margin of Yangtze Block.The new-discovered first stage deformation of those sequences occurred from the middle Triassic to the end of early Jurassic together with development of regional folding, which was resulted from the deep detachment shearing tending toward NW-WNW. The folds dip to east and fall down toward west, and were superimposed by the main stage folding.Thereafter, a series of folds were developed with axes trending toward northeast.Consequently normal folds occurred on the normal limbs while overturned fold on the overturned limbs during the first stage folding. The detachment or thrust was formed from late Jurassic to early Cretaceous. Due to the uplifting of Dabie and the Wannan Mountains in the north and south sides, the bi-directional thrusting belt was formed by gravity flowing from the Mountains toward the center of the basin along the north side of Xuancheng and south side of Guichi. The deformation geodynamics was discussed simply based on the newly recognized information about the tectonic evolution.展开更多
For 7475 Al alloy,there were micrographs showing filaments or whiskers formation during the separation stage of superplastic elongation.This indicates the presence of liquid phase which accommodates grain boundary sli...For 7475 Al alloy,there were micrographs showing filaments or whiskers formation during the separation stage of superplastic elongation.This indicates the presence of liquid phase which accommodates grain boundary sliding to reach superplasticity.On the other hand,there is no such phenomenon reported regarding Mg alloy in literatures.Scanning electron microscopic(SEM)fractography exceptionally exhibits a mark of grain boundary sliding and its accommodating mechanism of inter-granular liquid phase.Under the testing conditions of 350℃ and 1×10- 4s -1,the initially fine-grained structure(3.7μm)yields 642%superplastic elongation and exhibits fluffy appearance on the fractured surface.For other specimens showing less superplasticity,their fractured surfaces exhibit partial fluffy appearance.展开更多
文摘Aluminum-10% TiB master alloy was added in various proportions in 7178 Al alloy in order to examine the effect of TiB on grain refinement, wear and compressive deformation of the later one. Microstructural characterization reveals that TiB particles act as grain refiners for primary base alloy and result in globular dendrites. It was observed that the wear resistance and strength of the alloy decreased when the master alloy addition increased beyond 20%, even though the dendrites become much finer and almost spherical in nature.
文摘The AA6061-10 wt.%B4 C mono composite, AA6061-10 wt.%B4 C-Gr(Gr: graphite) hybrid composites containing 2.5, 5, and 7.5 wt.% Gr particles, and AA6061-10 wt.%B4 C-Mo S2 hybrid composites containing 2.5, 5, and 7.5 wt.% Mo S2 particles were fabricated through stir casting. The dry sliding tribological behaviors of the mono composite and hybrid composites were studied as a function of temperature on high temperature pin-on-disc tribotester against EN 31 counterface. The wear rate and friction coefficient of the Gr-reinforced and Mo S2-reinforced hybrid composites decreased in the temperature range of 30-100 ℃ due to the combined lubrication offered by the wear protective layer and its solid lubricant phase. Scanning electron microscopy(SEM) observation of the worn pin surface revealed severe adhesion, delamination, and abrasion wear mechanisms at temperatures of 150, 200, and 250 ℃, respectively. At 150 ℃, transmission electron microscopy(TEM) observation of the hybrid composites revealed the formation of deformation bands due to severe plastic deformation and fine crystalline structure due to dynamic recrystallization.
文摘Multistage superimposed deformation has been discussed systematically based on the progress of the stratigraphic sequences of the northeastern margin of Yangtze Block.The new-discovered first stage deformation of those sequences occurred from the middle Triassic to the end of early Jurassic together with development of regional folding, which was resulted from the deep detachment shearing tending toward NW-WNW. The folds dip to east and fall down toward west, and were superimposed by the main stage folding.Thereafter, a series of folds were developed with axes trending toward northeast.Consequently normal folds occurred on the normal limbs while overturned fold on the overturned limbs during the first stage folding. The detachment or thrust was formed from late Jurassic to early Cretaceous. Due to the uplifting of Dabie and the Wannan Mountains in the north and south sides, the bi-directional thrusting belt was formed by gravity flowing from the Mountains toward the center of the basin along the north side of Xuancheng and south side of Guichi. The deformation geodynamics was discussed simply based on the newly recognized information about the tectonic evolution.
文摘For 7475 Al alloy,there were micrographs showing filaments or whiskers formation during the separation stage of superplastic elongation.This indicates the presence of liquid phase which accommodates grain boundary sliding to reach superplasticity.On the other hand,there is no such phenomenon reported regarding Mg alloy in literatures.Scanning electron microscopic(SEM)fractography exceptionally exhibits a mark of grain boundary sliding and its accommodating mechanism of inter-granular liquid phase.Under the testing conditions of 350℃ and 1×10- 4s -1,the initially fine-grained structure(3.7μm)yields 642%superplastic elongation and exhibits fluffy appearance on the fractured surface.For other specimens showing less superplasticity,their fractured surfaces exhibit partial fluffy appearance.
