Peter Grünberg Institut PGI-5, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany.
Sci Rep. 2016 Jul 19;6:29700. doi: 10.1038/srep29700.
High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure.
高熵合金是目前受到高度研究关注的多组分金属材料。它们具有独特的化学无序和晶体长程有序的组合，由于其吸引人的特性，是技术应用的有前途的候选材料。许多高熵合金具有出人意料的高强度，偶尔还具有高延展性和低密度。影响这些有吸引力的机械性能的机制尚不清楚。本研究解决了 Al28Co20Cr11Fe15Ni26 高熵合金的变形机制问题，该合金是一种两相材料，由 B2 有序基体和无序体心夹杂组成。我们通过透射电子显微镜方法，包括弱束成像和会聚束电子衍射，对变形样品的微观结构和位错进行了定量分析。我们发现，B2 相中变形过程主要由在平面上滑动的螺位错的不均匀滑移控制。这些位错是 B2 晶格的完美超位错，没有解离。这表明结构中的反相晶界能非常高，抑制了位错核心的扩展。随着与位错相关的广泛扩展应变场的观察，我们的结果为该高熵合金的高强度提供了可能的解释，这是其位错结构的直接结果。
