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Deep Insights into the Twinning Mechanism in High-Performance Al Alloys: A Comprehensive First-Principles Study
Metallurgical and Materials Transactions A ( IF 2.8 ) Pub Date : 2021-01-21 , DOI: 10.1007/s11661-020-06134-z
Touwen Fan , Feng Liu , Zhipeng Wang , Linghong Liu , Dongchu Chen , Qihong Fang , Pingying Tang

The twinning mechanism of Al solid solutions is comprehensively investigated via the first-principles method. The relative stability of C and H atoms at tetrahedral and octahedral centers is discussed. Moreover, the interaction energies between solute atoms at different atomic layers and generalized stacking-fault structures are calculated. Results indicate that the stable occupation of C atom exists at the octahedral center rather than at the tetrahedral center. By contrast, the H atom stably exists at the tetrahedral center rather than at the octahedral center. Both atoms can effectively reduce the minimum energy barrier of dislocation nucleation, thereby promoting dislocation nucleation. The C atom more easily promotes dislocation nucleation than the H atom. Furthermore, both atoms are repelled by the stacking-fault plane. However, they are more likely to be segregated in the second neighboring layer of unstable stacking fault, intrinsic stacking fault (ISF), and unstable twinning fault (UTF) structures. Charge density measurements reveal that the twinning process is likely inhibited because of the strong local chemical bonding around the UTF layer from the ISF structure to the UTF structure. High concentrations of both atoms inhibit the twinning deformation at crack tips and grain boundaries, but they have almost no effect on the twinning deformation inside the grains. This study provides deep insights into the twinning deformation mechanism of face-centered-cubic alloy systems.



中文翻译:

高性能铝合金孪晶机理的深刻见解:全面的第一性原理研究

通过全面研究铝固溶体的孪生机理。第一原理方法。讨论了C和H原子在四面体和八面体中心的相对稳定性。此外,计算了不同原子层上的溶质原子与广义堆叠-断裂结构之间的相互作用能。结果表明,C原子的稳定占据存在于八面体中心而不是四面体中心。相反,H原子稳定地存在于四面体中心而不是八面体中心。两个原子都可以有效地降低位错成核的最小能垒,从而促进位错成核。C原子比H原子更容易促进位错成核。此外,两个原子都被堆垛层错面排斥。然而,它们更有可能被隔离在不稳定堆垛层错,固有堆垛层错(ISF)和不稳定孪生层错(UTF)结构的第二个相邻层中。电荷密度测量表明,孪生过程很可能受到抑制,因为从ISF结构到UTF结构的UTF层周围存在牢固的局部化学键。两个原子的高浓度都抑制了裂纹尖端和晶界处的孪生变形,但它们几乎对晶粒内部的孪生变形没有影响。这项研究为面心立方合金系统的孪生变形机理提供了深刻的见识。电荷密度测量表明,孪生过程很可能受到抑制,因为从ISF结构到UTF结构的UTF层周围存在牢固的局部化学键。两个原子的高浓度都抑制了裂纹尖端和晶界处的孪生变形,但它们几乎对晶粒内部的孪生变形没有影响。这项研究为面心立方合金系统的孪生变形机理提供了深刻的见识。电荷密度测量表明,孪生过程很可能受到抑制,因为从ISF结构到UTF结构的UTF层周围存在牢固的局部化学键。两个原子的高浓度都抑制了裂纹尖端和晶界处的孪生变形,但它们几乎对晶粒内部的孪生变形没有影响。这项研究为面心立方合金系统的孪生变形机理提供了深刻的见识。

更新日期:2021-01-21
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