Anin situ HVEM study of dislocation generation at Al/SiC interfaces in metal matrix composites
Anin situ HVEM study of dislocation generation at Al/SiC interfaces in metal matrix composites
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DOI：
10.1007/bf02643944
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发表时间：
1986-03
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影响因子：
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通讯作者：
M. Vogelsang;R. Arsenault;R. M. Fisher
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文献类型：
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作者：
M. Vogelsang;R. Arsenault;R. M. Fisher
退火后的铝/碳化硅 (Al/SiC) 复合材料表现出相对较高的位错密度，这些位错在铝基体中经常被细小的沉淀物修饰。这种高位错密度是这些复合材料具有意想不到的强度的主要原因。 Al 和 SiC 的热膨胀系数 (CTE) 之间的巨大差异 (10:1) 导致冷却过程中在 Al/SiC 界面处产生足够的应力，产生位错。在这项原位研究中，我们使用配备双倾斜加热台的高压电子显微镜 (HVEM) 观察了从退火温度冷却期间的位错产生过程。研究了两种类型的本体退火复合材料：一种具有不连续晶须形态的 SiC，另一种具有片状形态。此外，还检查了零体积百分比的对照样品。两种类型的复合材料均在 Al/SiC 界面处产生位错，导致密度至少为 1013m-2。从晶须端部观察的一个样品仅显示位错的重新排列，而当将相同材料切片以使晶须的长度位于箔平面内时，显示在冷却时在晶须末端产生位错。除了一些大的沉淀颗粒之外，对照样品在冷却时没有显示出位错的产生。结果支持这样的假设：在退火复合材料中观察到的高位错密度是 Al 和 SiC 不同热收缩的结果。 SiC 颗粒在从退火温度冷却期间充当位错源，导致高位错密度，从而强化材料。
ANNEALED aluminum/silicon carbide (Al/SiC) composites exhibit a relatively high density of dislocations, which are frequently decorated with fine precipitates, in the Al matrix. This high dislocation density is the major reason for the unexpected strength of these composite materials. The large difference (10:1) between the coefficients of thermal expansion (CTE) of Al and SiC results in sufficient stress to generate dislocations at the Al/SiC interface during cooling. In thisin situinvestigation, we observed this dislocation generation process during cooling from annealing temperatures using a High Voltage Electron Microscope (HVEM) equipped with a double tilt heating stage. Two types of bulk annealed composites were examined: one with SiC of discontinuous whisker morphology and one of platelet morphology. In addition, control samples with zero volume percent were examined. Both types of composites showed the generation of dislocations at the Al/SiC interface resulting in densities of at least 1013m-2. One sample viewed end-on to the whiskers showed only a rearrangement of dislocations, whereas, the same material when sectioned so that the lengths of whiskers were in the plane of the foil, showed the generation of dislocations at the ends of the whiskers on cooling. The control samples did not show the generation of dislocations on cooling except at a few large precipitate particles. The results support the hypothesis that the high dislocation density observed in annealed composite materials is a result of differential thermal contraction of Al and SiC. The SiC particles act as dislocation sources during cooling from annealing temperatures resulting in high dislocation densities which strengthen the material.