The hot deformation behavior of as-cast ZE41A magnesium alloy was studied by employing both processing maps and microstructural observations. To obtain processing map, hot compression tests were performed over a range...The hot deformation behavior of as-cast ZE41A magnesium alloy was studied by employing both processing maps and microstructural observations. To obtain processing map, hot compression tests were performed over a range of strain rates (0.001-1.0 s-1) and temperatures (250-450 ℃). Power dissipation efficiency (η) and instability parameter [ξ (ε)] were evaluated and processing maps were developed for the strain of 0.5. The dynamic recrystallization (DRX) and instable zones were identified and validated through micrographs. The processing maps can be used to select optimum strain rates and temperatures for effective hot working of the material.展开更多
In Stir cast Al 7075/20%SiCp composites were subjected to compression testing at strain rates and temperatures ranging from 0.001 to 1.0 s–1 and from 300°C to 500°C respectively. And the associated microstr...In Stir cast Al 7075/20%SiCp composites were subjected to compression testing at strain rates and temperatures ranging from 0.001 to 1.0 s–1 and from 300°C to 500°C respectively. And the associated microstructural transformations and instability phenomena were studied by observations of the optical electron microscope. The power dissipation efficiency and instability parameter were calculated following the dynamic material model and plotted with the temperature and logarithm of strain rate to obtain processing maps for strains of 0.5. The processing maps present the instability zones at higher strain rates. The result shows that with increasing strain, the instability zones enlarge. The microstructural examination shows that the interface separates even the particle cracks or aligns along the shear direction of the adiabatic shear band in the instability zones. The domain of higher efficiencies corresponds to dynamic recrystallization during the hot deformation. Using the processing maps, the optimum processing parameters of stain rates and temperatures can be chosen for effective hot deformation of Al 7075/20%SiCp composites.展开更多
Titanium matrix （Ti6Al4V） composites rein- forced with TiB2 and TiC were produced through powder metallurgy method. The effect of addition of both TiB2 and TiC with different contents （2.5 wt%, 5.0 wt% and 7.5 wt%...Titanium matrix （Ti6Al4V） composites rein- forced with TiB2 and TiC were produced through powder metallurgy method. The effect of addition of both TiB2 and TiC with different contents （2.5 wt%, 5.0 wt% and 7.5 wt%） on the density, microstructure and hardness properties of titanium matrix was investigated. The size distributions of the matrix alloy and reinforcement particles were measured by particle size analyzer. Microhardness of the sintered composites was evaluated using Vickers＇s hardness tester with a normal load of 3 N and a dwell time of 10 s. Ti6Al4V alloy and Ti6Al4V/TiB2-TiC composites were characterized through X-ray diffraction （XRD） and field emission scanning electron microscope （FESEM） equipped with energy-dispersive spectrometer （EDS）. The addition of TiB2 and TiC particles enriches the properties of Ti6Al4V alloy. The sintered Ti6Al4V/TiB2-TiC composite features a dense and pore-free microstructure with varying TiB2 and TiC particle distribution in the metal matrix. The results of this study show that the development of new phases plays a significant role in the properties of these composite materials.展开更多
文摘The hot deformation behavior of as-cast ZE41A magnesium alloy was studied by employing both processing maps and microstructural observations. To obtain processing map, hot compression tests were performed over a range of strain rates (0.001-1.0 s-1) and temperatures (250-450 ℃). Power dissipation efficiency (η) and instability parameter [ξ (ε)] were evaluated and processing maps were developed for the strain of 0.5. The dynamic recrystallization (DRX) and instable zones were identified and validated through micrographs. The processing maps can be used to select optimum strain rates and temperatures for effective hot working of the material.
文摘In Stir cast Al 7075/20%SiCp composites were subjected to compression testing at strain rates and temperatures ranging from 0.001 to 1.0 s–1 and from 300°C to 500°C respectively. And the associated microstructural transformations and instability phenomena were studied by observations of the optical electron microscope. The power dissipation efficiency and instability parameter were calculated following the dynamic material model and plotted with the temperature and logarithm of strain rate to obtain processing maps for strains of 0.5. The processing maps present the instability zones at higher strain rates. The result shows that with increasing strain, the instability zones enlarge. The microstructural examination shows that the interface separates even the particle cracks or aligns along the shear direction of the adiabatic shear band in the instability zones. The domain of higher efficiencies corresponds to dynamic recrystallization during the hot deformation. Using the processing maps, the optimum processing parameters of stain rates and temperatures can be chosen for effective hot deformation of Al 7075/20%SiCp composites.
文摘Titanium matrix （Ti6Al4V） composites rein- forced with TiB2 and TiC were produced through powder metallurgy method. The effect of addition of both TiB2 and TiC with different contents （2.5 wt%, 5.0 wt% and 7.5 wt%） on the density, microstructure and hardness properties of titanium matrix was investigated. The size distributions of the matrix alloy and reinforcement particles were measured by particle size analyzer. Microhardness of the sintered composites was evaluated using Vickers＇s hardness tester with a normal load of 3 N and a dwell time of 10 s. Ti6Al4V alloy and Ti6Al4V/TiB2-TiC composites were characterized through X-ray diffraction （XRD） and field emission scanning electron microscope （FESEM） equipped with energy-dispersive spectrometer （EDS）. The addition of TiB2 and TiC particles enriches the properties of Ti6Al4V alloy. The sintered Ti6Al4V/TiB2-TiC composite features a dense and pore-free microstructure with varying TiB2 and TiC particle distribution in the metal matrix. The results of this study show that the development of new phases plays a significant role in the properties of these composite materials.
