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BCC(体心立方)和FCC(面心立方)结构共存的高熵合金通常具有优异的综合力学性能, Al元素可以促进含Cu高熵合金由FCC向BCC结构转变. 本文基于Chan-Hilliard方程和Allen-Cahn方程, 建立Al xCuMnNiFe高熵合金三维相场模型, 模拟了Al xCuMnNiFe高熵合金( x= 0.4, 0.5, 0.6, 0.7)在823 K等温时效时纳米富Cu相的微观演化过程. 结果表明, Al xCuMnNiFe高熵合金时效时会产生两种复杂核壳结构: 富Cu核/B2 s壳以及B2 c核/FeMn壳, 通过讨论分析发现形成的B2 c对纳米富Cu相的形成起到抑制作用, 这种抑制作用随着Al元素的增加而变大; 结合经验公式做出Al xCuMnNiFe高熵合金富Cu相的屈服强度随时效时间的变化曲线, 得到峰值屈服强度的时效时间和合金体系, 可以为时效工艺提供参考.High-entropy alloys with BCC and FCC coexisting structures usually have excellent comprehensive mechanical properties, and Al element can promote the transformation of Cu-containing high-entropy alloys from FCC structure to BCC structure to obtain the BCC and FCC coexisting structures. In order to illustrate the process of phase separation of high entropy alloys, a low-cost Al-TM transition group element high-entropy alloy is selected in this work. Based on the Chan-Hilliard equation and Allen-Cahn equation, a three-dimensional phase field model of Al xCuMnNiFe high-entropy alloy is established, and the microscopic evolution of the nano-Cu-rich phase of Al xCuMnNiFe high-entropy alloy ( x= 0.4, 0.5, 0.6, 0.7) at 823 K isothermal aging is simulated. The results show that the Al xCuMnNiFe high-entropy alloy generates two complex core-shell structures upon aging: Cu-rich core/B2 sshell and B2 ccore/FeMn shell, and it is found through discussion and analysis that the formed B2 cplays an inhibitory role in the formation of the nano-Cu-rich phase, and that this inhibitory role becomes larger with the increase of Al element. Combining the empirical formula, the curve of yield strength of the Cu-rich phase varying with the aging time is obtained for the Al xCuMnNiFe high-entropy alloy, and the overall yield strength of the high-entropy alloy has a rising-and-then-falling trend with the change of time, and the aging time of the peak yield strength and the alloy system are obtained from the change of the curve, so that the best alloy system and aging time of the high-entropy alloy can provide a reference for aging process.
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Keywords:
- phase field method/
- high entropy alloy/
- Cu-rich phase/
- elastic energy
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Alloy system Al Cu Mn Ni Fe Al0.4Cu1.5Mn1Ni1Fe1.5 7.4 27.8 18.5 18.5 27.8 Al0.5Cu1.5Mn1Ni1Fe1.5 9.2 27.2 18.2 18.2 27.2 Al0.6Cu1.5Mn1Ni1Fe1.5 10.8 26.8 17.8 17.8 26.8 Al0.7Cu1.5Mn1Ni1Fe1.5 12.28 26.36 17.5 17.5 26.36 
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Alloy elements Cu Mn Ni Al ${D}_{i}^{0, \varphi }/{({10}^{-5}~{\rm{m} } }^{2}{\cdot}{ {\rm{s} } }^{-1}$) ${\rm{\alpha } }({\rm{B} }{\rm{C} }{\rm{C} })$ 4.70 14.90 14.00 53.50 ${\rm{\gamma } }({\rm{F} }{\rm{C} }{\rm{C} })$ 4.30 1.78 1.08 2.20 ${Q}_{i}^{0, \varphi }/{({10}^{5}~{\rm{J} }{\cdot}{\rm{m} }{\rm{o} }{\rm{l} } }^{-1}$) ${\rm{\alpha } }({\rm{B} }{\rm{C} }{\rm{C} })$ 2.44 2.63 2.64 2.71 ${\rm{\gamma } } ({\rm{F} }{\rm{C} }{\rm{C} } )$ 2.80 2.64 2.73 2.67 $ {D}_{i}^{0, \varphi } $-frequency factor; $ {Q}_{i}^{0, \varphi } $-diffusion activation energy 下载:
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Parameter type Parameter Value Unit Cahn-Hilliard model[55] $ {\kappa }_{c} $ $ 5.0\times {10}^{-15} $ ${\rm{J} \cdot}{ {\rm{m} } }^{2}{\cdot{\rm{m} }{\rm{o} }{\rm{l} } }^{-1}$ $ {\kappa }_{\eta } $ $ 1.0\times {10}^{-15} $ $ {\rm{J}}{\cdot{\rm{m}}}^{2}{\cdot{\rm{m}}{\rm{o}}{\rm{l}}}^{-1} $ $ Y $ $ 2.14\times {10}^{11} $ $ {\rm{P}}{\rm{a}} $ $ {V}_{{\rm{m}}} $ $ 7.09\times {10}^{-6} $ ${ {\rm{m} } }^{3}{\cdot {\rm{m} }{\rm{o} }{\rm{l} } }^{-1}$ $ W $ $ 5.0\times {10}^{3} $ ${\rm J} {\cdot} {\rm mol}^{-1}$ $ T $ 823 K Elasticity constant[56] $ {C}_{11}^{{\rm{m}}} $ 228 GPa $ {C}_{12}^{{\rm{m}}} $ 132 GPa $ {C}_{44}^{{\rm{m}}} $ 116.5 GPa $ {C}_{11}^{{\rm{p}}} $ 169 GPa $ {C}_{12}^{{\rm{p}}} $ 122 GPa $ {C}_{44}^{{\rm{p}}} $ 75.3 GPa Lattice misfit coefficient[55] $ {\varepsilon }_{{\rm{C}}{\rm{u}}}^{0} $ $ 3.29\times {10}^{-2} $ $ {\varepsilon }_{{\rm{M}}{\rm{n}}}^{0} $ $ 5.22\times {10}^{-4} $ $ {\varepsilon }_{{\rm{N}}{\rm{i}}}^{0} $ $ 4.75\times {10}^{-4} $ $ {\varepsilon }_{{\rm{A}}{\rm{l}}}^{0} $ $ 1.64\times {10}^{-4} $ Simulation parameters $ {\rm{d}}x $ 1 nm $ {\rm{d}}y $ 1 nm $ {\rm{d}}z $ 1 nm $ \Delta t $ 0.01 $ {\kappa }_{c}, {\kappa }_{\eta } $-gradient energy coefficient; $ Y $-average stiffness; $ {V}_{{\rm{m}}} $-molar volume; $ W $-structural transformation barriers; $ {C}_{11}^{{\rm{m}}}, {C}_{12}^{{\rm{m}}}, {C}_{44}^{{\rm{m}}} $-elastic constant of the matrix phase; $ {C}_{11}^{{\rm{p}}}, {C}_{12}^{{\rm{p}}}, {C}_{44}^{{\rm{p}}} $-elastic constant of the precipitated phase; $ {\varepsilon }_{i}^{0}(i={\rm{C}}{\rm{u}}, {\rm{M}}{\rm{n}}, {\rm{N}}{\rm{i}}, {\rm{A}}{\rm{l}}) $- lattice misfit coefficients of Cu, Mn, Ni, Al; $ {\rm{d}}x, {\rm{d}}y, {\rm{d}}z $ unit length of simulated meshes; $ \Delta t $-unit time step 下载:
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Alloy elements Al Cu Mn Ni Fe Al — –1 –19 –22 –11 Cu –1 — 4 4 13 Mn –19 4 — –8 0 Ni –22 4 –8 — –2 Fe –11 13 0 –2 — 下载:
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Alloy system t* $ {N}_{v} $/($ \times {10}^{23}{{\rm{m}}}^{-3}) $ f/% r/nm Strengthening/MPa Al0.4Cu1.5Mn1Ni1Fe1.5 4500 3.9291 0.0116 1.9148 1166 Al0.5Cu1.5Mn1Ni1Fe1.5 4500 4.0817 0.0123 1.9286 1188 Al0.6Cu1.5Mn1Ni1Fe1.5 5000 3.3951 0.0103 1.9343 1038 Al0.7Cu1.5Mn1Ni1Fe1.5 7500 4.04 0.031 2.63 775 Whenr$\; \leqslant \;$2 nm, it is a dislocation slicing mechanism, and whenr> 2 nm, it is a dislocation bypassing mechanism. 下载:
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