[SY-K5] Symposium K-5

[SY-K5] Effects of a bulk-region size in the first-principles tensile test of a grain boundary

^○Masanori Kohyama¹, Hao Wang², Shingo Tanaka¹ (1.AIST, Japan, 2.Shanghai Univ., China)

The first-principles tensile test (FPTT) of a grain boundary (GB) is a powerful tool to clarify intrinsic tensile strength and failure process of a GB, according to natural behaviors of electrons and atoms, corresponding to a slow tensile test at zero temperature [1]. This is quite effective to clarify the effects of segregated impurities [2]. This can provide intrinsic energy-strain and stress-strain curves of a GB, which should be useful to construct separation-energy curves for “cohesive zone model” in a continuum model as a multi-scale simulation technique. However, there are several unsolved issues in interpreting FPTT results compared to real mechanical properties of GBs. In the present study, we investigate the effects of the bulk-region size in the GB supercell, where usually two symmetric interfaces of a coincidence-site lattice (CSL) GB are alternately stacked between bulk slabs with some thickness. We show that the bulk-region thickness seriously affect the features of energy-strain and stress-strain curves around the failure point by comparing the FPTTs of the same Al GB with different bulk-region thicknesses, which are also analyzed by local-energy and local-stress techniques [3]. The difference is dominated by the relation between the Griffith and stress conditions for failure, depending on the bulk-region thickness. From this viewpoint, we re-interpret our previous FPTT results of Al GBs with various segregated impurities [2].

[1] M. Kohyama, Phil. Mag. Lett. 79, 659 (1999); Phys. Rev. B, 65, 184107 (2002)

[2] G. H. Lu et al., Phys. Rev. B, 73, 224115 (2006)

[3] H. Wang et al., Modell. Simul. Mater. Sci. Eng. 25, 015005 (2017)