(Fe60Mn20Cr10Ni10)95(AlSiC)5中熵合金的室温静动态力学性能研究

Study on the Static and Dynamic Mechanical Properties of (Fe60Mn20Cr10Ni10)95(AlSiC)5 Medium-Entropy Alloy at Room Temperature

摘要:

高熵合金以其独特的合金设计理念和优异的综合力学性能成为材料科学领域广泛研究的热点之一。然而，传统的高熵合金体系往往含有贵重的Co元素且倾向于以等原子比设计，这使得合金的成本大大提升，进而限制了合金的工业化应用。基于此，本文设计开发了无钴的(Fe60Mn20Cr10Ni10)95(AlSiC)5中熵合金，通过适当降低Cr、Ni元素和大幅提升Fe元素的含量，可以有效地降低合金成本；基于经典的热力学判据，微量添加Al、Si和C元素可以显著提升合金基体的固溶强化，同时引入一定的碳化物颗粒强化。结果表明，(Fe60Mn20Cr10Ni10)95(AlSiC)5中熵合金具有简单的面心立方（FCC）晶体结构，其相组成包含有无序的FCC固溶体和有序的M23C6碳化物。基于FCC/M23C6的立方体-立方体取向关系和近似共格的界面特征，(Fe60Mn20Cr10Ni10)95(AlSiC)5中熵合金在准静态下展现出了优异的室温塑性和加工硬化能力，其压缩屈服强度为360±10 MPa，而压缩应变甚至可以达到70%；合金的拉伸屈服强度为365±15 MPa，最大抗拉强度为715±25 MPa，同时还具有约为40%的断后延伸率。在动态加载条件下，合金表现出了明显的正应变率敏感性，其动态屈服强度为910±35 MPa，相比准静态加载约提升了153%。同时仍然表现出了可见的加工硬化行为，且在压缩应变约为40%时，合金没有发生明显的破坏。TEM分析表明，准静态加载下FCC基体内部可见的位错墙和位错胞以及M23C6与位错的交互作用促使合金表现出了优异的强塑性结合；动态条件下，变形孪晶、9R相、堆垛层错和Lomer-Cottrell锁的产生促使合金具备了多重的强韧化机制，这使得该合金在高速冲击下表现出了潜在的抗冲击损伤容限能力。

Abstract:

High-entropy alloys (HEAs) have become one of the hot topics in the field of materials science due to their unique alloy design concepts and excellent comprehensive mechanical properties. However, traditional HEAs often contain valuable Co elements and tend to be designed in equal atomic ratios, which greatly increases the alloy costs and limits their industrial applications. Based on this, a cobalt-free (Fe60Mn20Cr10Ni10)95 (AlSiC)5 medium-entropy alloy (MEA) is established. By moderately decreasing Cr and Ni while obviously increasing Fe elements, the alloy cost can be effectively reduced. Relying on the classical thermodynamic criteria and minor additions of Al, Si, and C elements, the solid-solution strengthening can be significantly improved as well as a certain carbide particle strengthening. The results reveal that the current alloy exhibits a simple face-centered-cubic (FCC) crystal structure, with a phase composition consisting of disordered FCC solid solution and ordered M23C6 carbides. Based on the cube-cube orientation relationship and almost coherent interface characteristics of FCC/M23C6, the (Fe60Mn20Cr10Ni10)95 (AlSiC)5 MEA exhibits excellent room-temperature plasticity and work-hardening ability under quasi-static conditions, with a compressive yield strength of about 360±10 MPa and a compressive strain of up to 70%. Moreover, the alloy undergoes a tensile yielding strength of 365±15 MPa, an ultimate tesnsile strength of 715±25 MPa, as well as about 40% fracture to elongation. Upon dynamic loading, the alloy exhibits a positive strain-rate sensitivity, with a dynamic yield strength of approximately 910±35 MPa, which is about 153% higher than that of quasi-static loading. Meanwhile, it still exhibits visible work hardening and even at the strain of about 40%, the alloy still does not undergo significant damage. TEM analysis shows that visible dislocation walls and cells inside the FCC matrix, as well as the interaction between M23C6 and dislocations, lead to an excellent strength-plasticity combination under quasi-static loading. The formation of deformation twins, 9R phase, stacking faults, and Lomer-Cottrell locks provides the alloy with multiple strengthening and toughening mechanisms, thus yielding the potential damage tolerance capacity upon high-speed loading.