用透射电子显微术(包括弱束技术)对WC-12％Co硬质合金的形变和裂纹扩展过程及粘结相的相变机制进行了电子衍衬研究。研究指出:合金的形变行为取决于粘结相Co的协调应变的能力,裂纹扩展的特征形貌和WC及Co相的滑移结构及界面的性质有直接关系。裂纹在WC中、在WC/WC以及WC/Co界面呈直线传播,而在粘结相中则表现为“Z”字形特征。β-Co(fcc结构)在室温下不稳定,在不大的相变驱动力(例如,合金承受形变)作用下,很容易向hcp结构的ε-Co转变。这种转变的过程是:经由β-Co中的层错片加厚和长大,最终形成稳定的hcp结构ε-Co。
The diffraction contrast study was carried out on the deformation and the crack propagation process of WC-12%Co cemented carbide and on the mechanism of phase transformation of binder Co by TEM including weak-beam technique. It indicates that the deformation behaviour of the alloy depends upon the coordinating strain ability of binder Co, and that the characteristic morphology of the crack propagation seems to bear a direct relation to the slip structure of WC with binder Co and the properties of interfaces. The cracks propagate linearly along the intra- and transgranular fracture of WC,WC/WC and along WC/Co interface as well, but zigzaggedly in the binder Co. The β-Co (fee) is unstable at room temperature and very easy to transform into ε-Co (hcp) even by a smaller driving force of the phase transformation, e. g. the alloy subjected to deformation. It may be believed that this transformation undergos the growth and thickening of the stacking faults lamellae in the β-Co and thereby the formation of a stable ε-Co of hcp structure finally.
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