选区激光熔化AlCoCrCuFeNi高熵合金的高温氧化行为研究

High-temperature Oxidation Behaviors of AlCoCrCuFeNi High-entropy Alloys Prepared by Selective Laser Melting

摘要:

基于选区激光熔化技术制备了AlCoCrCuFeNi高熵合金,研究了其显微组织及800℃、1000℃和1200℃环境下的高温氧化行为,采用X射线衍射仪和扫描电镜等方法表征分析了氧化膜的物相组成和形貌特征。结果表明：所制备的AlCoCrCuFeNi高熵合金主要包含BCC相、BCC/B2相和少量的FCC相,显微组织为长直柱状枝晶和等轴胞晶结构组成的非平衡异质结构。AlCoCrCuFeNi高熵合金在三种温度下的高温氧化性能优异,氧化动力学曲线基本符合抛物线定律,氧化速率对温度有明显的依赖性,其随着温度的提高而增加,并且氧化反应导致氧化膜中产生了明显的空洞和裂纹,为金属元素的持续扩散提供了通道,加剧了氧化反应,所引起的剥落现象愈加严重,氧化膜主要成分为Cr₂O₃、Al₂O₃和MCr₂O₄尖晶石混合氧化物,较为致密的氧化膜可以有效地抑制基体受到进一步氧化,提高抗氧化性能。

Abstract:

AlCoCrCuFeNi high-entropy alloys (HEAs) were prepared by selective laser melting (SLM). The microstructure and high-temperature oxidation behaviors at 800℃, 1000℃ and 1200℃ were studied. The phase compositions and morphological characteristics of the oxide film were analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM). Results indicate that the prepared AlCoCrCuFeNi HEA mainly contains BCC phase, BCC/B2 phase and a small amount of FCC phase, and the microstructure is a non-equilibrium heterostructure composed of long straight columnar dendrite and equiaxed cell structures. The HEAs have good oxidation resistance at three temperatures. The oxidation kinetics curves basically follow the parabolic law. The oxidation rate is determined by a clear dependence on temperature, which increases with the increase of temperature, and obvious voids and cracks appear in the oxide films, which provided channels for diffusion of elements that aggravate the oxidation reaction, resulting in the oxide film peeling becomes more and more serious. The main components of the oxide films are Cr₂O₃, Al₂O₃ and spinel MCr₂O₄ mixed oxides. The denser oxide film can effectively inhibit the matrix from being further oxidized and improve the anti-oxidant properties of SLM-prepared HEA.