Controlled Diffusion Solidification(CDS) is a promising process relied on mixing two liquid alloys of precisely controlled chemistry and temperature in order to produce a predetermined alloy composition. In this study...Controlled Diffusion Solidification(CDS) is a promising process relied on mixing two liquid alloys of precisely controlled chemistry and temperature in order to produce a predetermined alloy composition. In this study, the CDS was employed to prepare hypereutectic Al-20%Si(mass fraction) alloy using Al-30%Si and pure Al of different temperatures. The mixing rate was controlled using three small crucibles with a hole of different diameters in their bottom. The effect of mixing rate and temperature on the microstructure of the primary Si-phase during the mixing of molten Al and Al-30%Si was studied. The results showed that when the diameter of the small crucible bottom hole is 16 mm, a higher mass mixing rate 0.217 kg·s-1 would results in a lower stream velocity 0.414 m·s-1. Conversely a lower mass mixing rate 0.114 kg·s-1(the diameter of the small crucible bottom hole is 8 mm) would result in a higher fluid stream velocity 0.879 m·s-1. A lower mass mixing rate would be better to refine the primary Si than a higher mass mixing rate. Meanwhile, the morphology and distribution of primary Si could also be improved. Especially, when Al-30%Si alloy at 820 °C was mixed with pure Al at 670 °C in the case of a mass mixing rate of 0.114 kg·s-1 and a pouring temperature of 680 °C, the average size of the primary Si phase would be only 18.2 μm. Its morphology would mostly be octahedral and the primary Si would distribute uniformly in the matrix microstructure. The lower mass mixing rate(0.114 kg·s-1) will enhance the broken tendency of Al-30%Si steam and the mixing agitation of resultant melt, so the primary Si phase can be better refined.展开更多
为了获得高分辨力TDICCD成像系统中高速视频处理器芯片的性能指标和成像效果,分析了成像系统视频处理器的参数设置、系统噪声类型和处理方法,设计了基于FPGA的LM98640芯片智能控制功能,实现了高分辨力TDICCD视频信号的分时采样量化和精...为了获得高分辨力TDICCD成像系统中高速视频处理器芯片的性能指标和成像效果,分析了成像系统视频处理器的参数设置、系统噪声类型和处理方法,设计了基于FPGA的LM98640芯片智能控制功能,实现了高分辨力TDICCD视频信号的分时采样量化和精确采样调节控制功能,降低了TDICCD相机电子学系统的噪声水平,提高了信噪比指标。经实验对比分析,基于LM98640的TDICCD视频信号处理系统,能有效提高像元处理速度和图像数据精度,成像系统输出图像信噪比可达到47.4 d B。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51064017 and 51464031)
文摘Controlled Diffusion Solidification(CDS) is a promising process relied on mixing two liquid alloys of precisely controlled chemistry and temperature in order to produce a predetermined alloy composition. In this study, the CDS was employed to prepare hypereutectic Al-20%Si(mass fraction) alloy using Al-30%Si and pure Al of different temperatures. The mixing rate was controlled using three small crucibles with a hole of different diameters in their bottom. The effect of mixing rate and temperature on the microstructure of the primary Si-phase during the mixing of molten Al and Al-30%Si was studied. The results showed that when the diameter of the small crucible bottom hole is 16 mm, a higher mass mixing rate 0.217 kg·s-1 would results in a lower stream velocity 0.414 m·s-1. Conversely a lower mass mixing rate 0.114 kg·s-1(the diameter of the small crucible bottom hole is 8 mm) would result in a higher fluid stream velocity 0.879 m·s-1. A lower mass mixing rate would be better to refine the primary Si than a higher mass mixing rate. Meanwhile, the morphology and distribution of primary Si could also be improved. Especially, when Al-30%Si alloy at 820 °C was mixed with pure Al at 670 °C in the case of a mass mixing rate of 0.114 kg·s-1 and a pouring temperature of 680 °C, the average size of the primary Si phase would be only 18.2 μm. Its morphology would mostly be octahedral and the primary Si would distribute uniformly in the matrix microstructure. The lower mass mixing rate(0.114 kg·s-1) will enhance the broken tendency of Al-30%Si steam and the mixing agitation of resultant melt, so the primary Si phase can be better refined.
文摘为了获得高分辨力TDICCD成像系统中高速视频处理器芯片的性能指标和成像效果,分析了成像系统视频处理器的参数设置、系统噪声类型和处理方法,设计了基于FPGA的LM98640芯片智能控制功能,实现了高分辨力TDICCD视频信号的分时采样量化和精确采样调节控制功能,降低了TDICCD相机电子学系统的噪声水平,提高了信噪比指标。经实验对比分析,基于LM98640的TDICCD视频信号处理系统,能有效提高像元处理速度和图像数据精度,成像系统输出图像信噪比可达到47.4 d B。
