快速凝固AlCoCrFeNi2.1共晶高熵合金的微观组织演变和力学性能

使用真空快速凝固设备制备不同直径的AlCoCrFeNi_2.1合金铸棒和薄带，研究了冷却速率对多主元共晶高熵合金的微观组织和力学性能的影响。结果表明，全部试样均由FCC和B2两相组成。不同直径的合金铸棒均为常规共晶组织，只在表层某些位置观察到胞状共晶组织。铸棒的直径越小，冷却速率越大，规则共晶组织的片间距(λ)越小，其屈服强度越高。当铸棒直径由8 mm减小至2 mm时表层区域的λ值由530.4 μm减小至357.0 μm，轴心区域的片间距由712 μm减小至474 μm，合金的屈服强度由690 MPa提高到877 MPa。结合合金薄带的微观组织分析结果表明，随着冷却速率的提高AlCoCrFeNi_2.1合金依次形成规则和非规则混合共晶组织、胞状共晶组织和树枝状组织。

Microstructure Evolution and Mechanical Properties of Rapid Solidified AlCoCrFeNi2.1 Eutectic High Entropy Alloy

Rods with different diameters and ribbons of the multi-component eutectic high-entropy alloy AlCoCrFeNi_2.1 were prepared by vacuum rapid solidification facility. The effect of cooling rate on microstructure and mechanical properties of the alloy was investigated. The results show that all of the alloys consist of FCC and B2 phases. Alloy rods of different diameters present a typical eutectic structure, with the presence of the cellular microstructure at certain sites of axial surface regions. The decrease of the diameter raises the cooling rate of the casting rod, resulting in the decrease of lamellar spacing (λ) of the regular eutectic structure and the increase of yield strength. As the diameter decreases from 8 mm to 2 mm, the values of λ decrease from 530.4 to 357.0 μm in the axial surface regions and from 712.0 μm to 474.0 μm in the axial center regions, resulting in the increase of the yield strength from 690 MPa to 877 MPa. As far as the microstructure morphology of the alloy ribbons is concerned, it can be concluded that the microstructure of the alloy may evolves in the following sequence, namely, regular and irregular eutectic structure, cellular structure and dendrite structure as the cooling rate is increased.