尺寸高稳定性复合材料桁架结构的研制

介绍了某卫星复合材料桁架结构的研制情况,通过材料选择、铺层设计、材料的热膨胀系数测试与分析,制造了高精度的复合材料桁架,并测量了结构的热变形。测量结果表明:采用高模量碳纤维复合材料能够制造出热变形只有微米级的高稳定结构。这是针对超稳卫星平台所需的尺寸高稳定性结构的首次成功探索。文章最后对进一步降低结构热变形、提高尺寸稳定性和测量精度提出了建议。     

Microstructure and Hot Deformation Behavior of Mg-9Al-3Si-0.375Sr-0.78Y Alloy

Using Gleeble-3500 thermal simulator, the high temperature plastic deformation behavior and microstructure evolution of Mg-9Al-3Si-0.375Sr-0.78Y alloy are investigated at the temperature of 523 K?673 K and the strain rate of 10-3 s-1?10 s-1. True strain-true stress curves show the characteristics of the typical dynamically recrystallization process. The Arrhenius constitutive equation of the hyperbolic model is established. The average activation energy and the strain rate sensitivity index are, respectively, 221.578 kJ.mol-1 and 0.137. The result shows that the α-Mg phase exhibits dynamic recrystallization (DRX) characteristics obviously. But no DRX occurs in theβ-Mg17Al12 phase. Hot deformation does not affect the primary Mg2Si phase. Under the conditions of low temperature (523 K?673 K) and high strain rate (1 s-1?10 s-1), the flow instability and macro-defects such as crack appear in the specimens. However, there are finer recrystallization grains. Under the conditions of high temperature (≥673 K) or low strain rate, the microstructure of the alloy shows good homogeneity. The size of the primary Mg2Si phase is uniform, the size of the β-Mg17Al12 phase is small, and the distribution of the β-Mg17Al12 phase is uniform.     

Study on the Deformation Behavior of Mg-Gd-Y-Zn-Mn Wrought Magnesium Alloys by Visco-plastic Self-consistent Modeling

The plastic deformation behavior of new Mg-Gd-Y-Zn-Mn magnesium alloys gains great necessity to clarify and understand the mechanism deeply. In the present work, the tensile mechanical property test and visco-plastic self-consistent (VPSC) model are used to investigate the activities of deformation modes of VW84M and VW94M magnesium alloys during the tensile deformation. The results show that the mechanical properties of the above extruded alloys are similar but VW94M has higher strength than VW84M after the same aging process. Compared with the extruded alloys, the as-aged alloys have significantly higher activation of pyramidal slip at the later stage of plastic deformation. In addition, the as-aged VW94M alloy with higher strength has the largest activity of pyramidal slip. In summary, the addition of Gd increases the critical resolved shear stress (CRSS) in each slip system of VW94M, while the increase in the strength and the decrease in the elongation of as-aged alloys are associated with the significant activation of pyramidal slip.     

航空航天用高强度Mg-RE系合金的研究进展

近年来,镁稀土合金由于其高强度、低密度和高温性能良好等特点,在追求轻量化的航空航天产业当中受到越来越多的关注。总结当前主流的2系高强度Mg-RE合金(Mg-Gd和Mg-Y系合金)的性能特点、强化机制和研究进展,简要介绍其他Mg-RE合金的研究情况,最后回顾镁稀土合金在航空航天领域的应用。     

碳/环氧编织复合材料热膨胀特性分析

采用理论与试验相结合的方法,研究了碳/环氧三维编织复合材料的热膨胀特性。通过试验方法获得了不同规格的三维编织复合材料在编织方向的热膨胀系数,并基于均匀化理论建立了编织材料热弹性性能的分析方法,对数值结果与试验值进行了比较。研究表明,三维编织复合材料在编织方向上具有典型的负膨胀特性;与三维四向编织结构复合材料相比,三维五向编织结构复合材料具有较小的负膨胀系数;三维编织复合材料编织方向的负膨胀系数随着纤维体积含量的增大而减小,随着编织角的增大而增大;基于均匀化理论的热弹性数值分析方法可有效地预报三维编织复合材料的等效热膨胀系数,数值计算值与试验结果吻合较好。     

轻型高强Al-Si/SiC复合材料反射镜的制备与性能

文章采用反应烧结工艺制备 Si/SiC 材料,然后通过真空扩散渗铝工艺制备了 Al-Si/SiC 复合材料。通过精确调控浸渗合金的铝浓度使制备的Al-Si/SiC复合材料具有可控的热膨胀系数,利用该工艺制备出热膨胀系数连续可调（4.6×10-6K-1~8.7×10-6K-1,0~40℃）的 Al-Si/SiC 复合材料,其力学性能优异,经检测密度为2.86g/cm3,弹性模量为236GPa,断裂韧性为6.1MPa＆#183;m1/2,可采用线切割、铣磨、钻孔、攻丝等手段加工,相比SiC陶瓷材料更易于高精度机械加工。扫描电子显微镜分析表明,制备的Al-Si/SiC复合材料均匀、致密,光学抛光后表面粗糙度均方根值达到1.017 nm。各项测试数据表明, Al-Si/SiC复合材料作为反射镜可以满足空间光学的应用。     

真空热试验中冷能利用的思考

在大型航天器的真空热试验中,仅从过冷器排除的液氮和低温气氮的混合物就达约5×104kg,其中蕴涵了108kJ量级的冷能.文章首先介绍了自然冷能和LNG冷能利用的研究现状,并结合航天器真空热试验的实际情况,研究了试验过程中排气造成的冷能损失,对它的再利用可行性进行了讨论,提出可以采用联合法冷能回收流程,并提出了冷能利用中的几个关键问题.认为:需要解决液氮和低温气氮供应的连续性及找到恰当的二次冷媒,是真空热试验中冷能利用的关键.