Cemented carbides are hard materials used for the fabrication of cutting tools. They consist of hard micron or sub-micron carbide grains held together in a matrix of a tough metallic binder such as cobalt. The understanding and control of cobalt characteristics are of crucial importance to improve the mechanical properties of WC-Co cemented carbide materials. Indeed, cobalt controls the toughness of the material and its properties seem to condition the durability of cemented carbides. At low temperature, pure cobalt is normally found in hcp structure, while above 426 °C (700 K) it changes to fcc crystalline structure. Remarkably, in cemented carbides, cobalt appears even at low temperature as fcc, otherwise as a mixture of fcc and hcp. It is unsure if these crystal structures are due to the presence of internal stresses or due to W and C soluted atoms. However, this paper demonstrates that cobalt in WC-10wt.%Co cemented carbide may show some characteristics of a glass transition at around 669 °C (942 K) in the 1 Hz frequency range, inducing a glassy state to cobalt, which is of great interest from a fundamental point of view, however challenging to control in materials technology.

硬质合金是用于制造切削工具的硬质材料。它们由硬的微米级或亚微米级的碳化物晶粒组成，这些晶粒在坚硬的金属粘合剂（例如钴）的基质中保持在一起。理解和控制钴的特性对于改善WC-Co硬质合金材料的机械性能至关重要。确实，钴控制着材料的韧性，其性能似乎决定了硬质合金的耐久性。在低温下，通常在hcp结构中发现纯钴，而在426°C（700 K）以上时，它变为fcc晶体结构。值得注意的是，在硬质合金中，即使在低温下，钴也以fcc的形式出现，否则会以fcc和hcp的混合物形式出现。不能确定这些晶体结构是由于内部应力的存在还是由于W和C溶化了的原子。但是，本文证明WC-10wt。％Co硬质合金中的钴可能在1 Hz频率范围内在669°C（942 K）时显示出玻璃化转变的某些特征，从而导致玻璃态转变为钴。从基本的角度来看，人们非常感兴趣，但是在材料技术上进行控制具有挑战性。