Investigating size dependence in nanovoid-embedded high-entropy-alloy films under biaxial tension
Investigating size dependence in nanovoid-embedded high-entropy-alloy films under biaxial tension
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DOI：
10.1007/s00419-021-02100-2
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发表时间：
2022-01
影响因子：
2.8
通讯作者：
Yi Cui;Zengtao Chen;Shaojie Gu;Wenzhi Yang;Yang Ju
中科院分区：
文献类型：
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作者：
Yi Cui;Zengtao Chen;Shaojie Gu;Wenzhi Yang;Yang Ju
研究了高熵合金（HEA）单晶和多晶薄膜在双轴拉伸下中心纳米孔洞的尺寸依赖性。关于单晶样品，我们的注意力是支付在嵌入式纳米空隙不变的空隙体积分数（VVF）的比例增加。在双轴拉伸条件下，位错开始从空洞发射的临界应力由大到小依次为CoCrFeCuNi < CoCrFeMnNi <金属Ni。晶格畸变有利于位错从空洞表面发射，与理论模型相比，降低了临界应力。对于多晶样品，薄膜和嵌入式纳米空隙的尺寸保持不变，而允许周期性六边形或随机生成的晶粒尺寸变化。除CoCrFeCuNi随机多晶外，其余多晶样品的峰值应力服从逆Hall-Petch效应。单晶和多晶CoCrFeMnNi样品由于与成核二次空隙的聚结而失败。对于后者，晶界作为二次空隙成核的主要场所。与HEAs不同，多晶Ni样品由于晶间开裂而不是空隙生长和聚结而失败。
The size dependence of central nanovoid embedded in either monocrystalline or polycrystalline high-entropy-alloy (HEA) films under biaxial tension is investigated in this study. Regarding monocrystalline samples, our attention is paid to the proportional increase in the embedded nanovoid with invariant void volume fraction (VVF). The critical stresses in concerned materials at which dislocations start to emit from void under biaxial tension, in an ascending order, are CoCrFeCuNi < CoCrFeMnNi < metal Ni. Lattice distortion appears to facilitate dislocation emission from the void surface in HEAs, which lowers the critical stress compared with the theoretical model. Regarding polycrystalline samples, the size of both the film and embedded nanovoid is kept invariant, whereas grain size of either periodic hexagonal ones or randomly generated ones is allowed to vary. Apart from the random polycrystalline CoCrFeCuNi, the peak stresses of rest polycrystalline samples obey the reverse Hall–Petch effect. Both monocrystalline and polycrystalline CoCrFeMnNi samples fail due to the coalescence with nucleated secondary voids. For the latter, grain boundaries act as primary sites for secondary void nucleation. Unlike HEAs, polycrystalline Ni samples fail due to intergranular cracking instead of void growth and coalescence.