Schuh Benjamin, Völker Bernhard, Todt Juraj, Kormout Karoline S, Schell Norbert, Hohenwarter Anton
Department of Materials Physics, University of Leoben, Jahnstraße 12, 8700 Leoben, Austria.
Materials Chemistry, RWTH Aachen University, Kopernikusstrasse 10, 52074 Aachen, Germany.
Materials (Basel). 2018 Apr 24;11(5):662. doi: 10.3390/ma11050662.
An equiatomic CrCoNi medium-entropy alloy was subjected to high-pressure torsion. This process led to a refinement of the microstructure to a grain size of about 50 nm, combined with a strong increase in the materials hardness. Subsequently, the thermodynamic stability of the medium entropy alloy was evaluated by isothermal and isochronal heat treatments. Annealed samples were investigated by scanning and transmission electron microscopy as well as X-ray diffraction, and were subjected to tensile tests to establish microstructure-property relationships. Furthermore, a comparison of mechanical properties with a grade 316L stainless steel was performed in order to evaluate if the CrCoNi alloy is competitive with commercially available structural materials in the nanocrystalline state. A minority phase embedded in the face-centered cubic matrix of the CrCoNi alloy could be observed in multiple annealed states, as well as the as-received and high-pressure torsion processed material. For 200 h of annealing at 500 °C, it was determined that the minority phase has a hexagonal-closed-packed crystal structure. A possible explanation for the formation of the phase is a preferential segregation of Co to stacking faults.
对一种等原子CrCoNi中熵合金进行了高压扭转处理。这一过程导致微观结构细化至约50纳米的晶粒尺寸，同时材料硬度大幅增加。随后，通过等温及等时热处理评估了该中熵合金的热力学稳定性。对退火后的样品进行了扫描电子显微镜、透射电子显微镜以及X射线衍射分析，并进行拉伸试验以建立微观结构与性能的关系。此外，与316L不锈钢进行了力学性能比较，以评估CrCoNi合金在纳米晶态下是否能与市售结构材料竞争。在多种退火状态以及原始态和高压扭转处理后的材料中，均可观察到嵌入CrCoNi合金面心立方基体中的少数相。对于在500℃下退火200小时的情况，确定少数相具有六方密排晶体结构。该相形成的一种可能解释是Co优先偏聚到堆垛层错处。
