State Key Laboratory of Superhard Materials, Department of Materials Science and Key Laboratory of Automobile Materials, MOE , Jilin University , Changchun 130012 , People's Republic of China.
Department of Materials , Imperial College London , London SW7 2AZ , United Kingdom.
ACS Appl Mater Interfaces. 2018 May 9;10(18):16124-16132. doi: 10.1021/acsami.8b02338. Epub 2018 Apr 30.
As structural materials, crystalline or metallic glass materials have attracted scientific and practical interests. However, some mechanisms involving critical size and shear bands have adverse effects on their mechanical properties. Here, we counter these two effects by introducing a special structure with ultrafine ceramic grains (with a diameter of ∼2.0 nm) embedded into a metallic glass matrix, wherein the grains are mainly composed of a Ta-W-N solid solution structure in nature, surrounded by a W-based amorphous matrix that contains Ta and N atoms. Such a structure is in situ formed during preparation, which combines the merits of both phases to achieve simultaneous increase in hardness and toughness relative to references (pure TaN and W) and thus superior wear resistance. Even more remarkable, a favorable variation of increased hardness but reduced elasticity modulus can be induced by this structure. Intrinsically, ultrafine ceramic grains (free of dislocations), embedded in the metallic glass matrix, could prevent shear band propagation within the glass matrix and further improve the hardness of the matrix material. In return, such glass matrix allows for stiffness neutralization and structural relaxation to reduce the elasticity modulus of ceramic grains. This study will offer a new guidance to fabricate ultrahigh-performance metal-based composites.
作为结构材料，晶态或金属玻璃材料引起了科学界和工业界的广泛关注。然而，一些涉及临界尺寸和剪切带的机制对它们的力学性能有不利影响。在这里，我们通过引入一种特殊结构来克服这两个效应，该结构具有嵌入金属玻璃基体中的超细陶瓷颗粒（直径约为 2.0nm），其中颗粒主要由 Ta-W-N 固溶体结构组成，周围是含有 Ta 和 N 原子的 W 基非晶基体。这种结构是在制备过程中原位形成的，结合了两相的优点，相对于参考材料（纯 TaN 和 W）实现了硬度和韧性的同时提高，从而具有优异的耐磨性。更值得注意的是，这种结构可以诱导硬度增加而弹性模量降低的有利变化。本质上，嵌入金属玻璃基体中的超细陶瓷颗粒（无位错）可以阻止剪切带在玻璃基体中的传播，从而进一步提高基体材料的硬度。反过来，这种玻璃基体允许刚度中和和结构松弛，从而降低陶瓷颗粒的弹性模量。本研究将为制备超高性能金属基复合材料提供新的指导。
