不同冷却条件SiCp／ZA—27复合材料界面的TEM观察

主要用透射电子显微技术（TEM）、电子探针显微分析（EPMA）和选区电子衍射技术（SAD）分析了不同冷却条件下SiCp/ZA-27复合材料的界面特征和结构，发现冷却速度明显影响复合材料的界面结构、界面相组成和复杂金属氧化物的分布以及枝晶生长过程的溶质二次分配，且复合材料慢冷时的界面比液淬时的界面复杂得多。复合材料浆液液淬快冷时的界面特征是初生α（Al)相与 SiC颗粒直接机械结合，界面光滑无界面反应产物和中间过渡相及非晶氧化物；电磁搅拌随炉冷却条件下，复合材料界面绝大部分是共晶组织与SiC颗粒直接结合，少部分是由共晶组织／岛状非晶组织／SiC组成；随炉慢冷时的界面主要是由共晶组织／非晶组织／SiC组成，金属基体与SiC直接结合的界面非常少。不同冷却条件制备的复合材料的界面存在不同厚度的非晶组织。根据界面形貌和选区电子衍射花样并结合计算机模拟计算，发现部分界面处存在第三相（如MgAl2O3,Mg6Cu3Al7等相），合成电子衍射花样表明这些第三相与SiC或基体间无晶体学位相关系。未发现SiC与基体间有晶体学位相关系，说明α（Al)或共晶相在SiC或基体间无晶体学位相关系。未发现SiC与基体间有晶体学位相关系，说明a(Al)或共晶相在SiC表面成核的可能性较小。复合材料浆液水淬后的基体轻微衍射分析得出饱和a(Al)已发生分解反应，由白色稳定的af相和黑色中间过渡相α′及存在于黑色区域中的η相组成，af与a′的晶格常数有微小差异，晶体结构相同，两相具有良好的共格关系。η相与af的位相关系为：[-1-10]α//[-12-10]η,(1-11)a//(0002)η。

TEM Observation of SiCp/ZA-27 Composite Interfaces in Different Cooling Conditions

The interface structure and characteristics of SiCp-27 composites prepared in different cooling conditions were investigated by using transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and selected-area diffraction(SAD) methods. The results showed that the cooling velocities obviously affect the interface structures, the constituents of interface phases, the distribution of metal oxides and the re-distribution of solutes ejected by the growth of dendritic crystal. The interface of the composites in slow cooling was much more complicated than that in quenched state. The interfaces that the composite slurry was quenched in water were characterized of directly mechanical handing, planar interface, no reaction products and no mediantransition phases. The interface that the composite slurry was stirred as the slurry was cooled in the furnace mastly consisted of directly bonding of SiC and the eutecticum, and a little part consisted of the matrix/island- shapedamorphous solid/SiC. The interfaces of the composite that directly eded in the furnace mainly consisted of the eutecticum/ amorphous solid/ SiC, and a little part consisted of directly bonding of SiC and the matrix. The depth of the amorphous solid around SiC varied with eding conditions. According to the interface morphology, selected area diffraction patterns and computer simulation, some third phases were found, such as MgAl2O4 (Spinel) and Mg6Cu3Al7 at or near the interface. The composite diffraction patterns of the third phases and SiC or the matrix showed that there were no crystallographic orientation relationships (CORs). The COR between SiC and the matrix has not been resolved. It demonstrated that there was a little possibility that primary a(A1) or eutectic constituents can nucleate on SiC. It was confirmed by micros -diffraction technique that the matrix of the composites quenched in water was decomposed and consisted of stable phase af (white), transition phase a' (black) and phase in the black zone. af and a' phase had the same crystalline structure and good coherent relationship, but a little difference in lattice spacing. A crystallographic orientation relationship between af and [- 1 - 10]a//[ ~ 12~ 10] , (1 ~ 11)a//(0 0 0 2) was confirmed.