MAEAM investigation of the structural stability and theoretical strength of Fe crystals under uniaxial loading

Abstract

The structural stability and theoretical strength of BCC crystal Fe under uniaxial loading have been investigated with the modified analytic embedded-atom method (MAEAM). Even if an orthorhombic path is applied, the deformation is spontaneous along the tetragonal path till Milstein modified Born criterion B 22 -B 23 >0 is violated at λ 1 =0.9064 in the compressive region. The branched orthogonal path with lower compressive stress σ 1 and energy E is preferred over the conventional tetragonal Bain path. A stress-free FCC phase with the local maximum energy of -4.2186eV appearing either in compressive region (orthorhombic path) at λ 1 =0.8923 or in tensile region (tetragonal path) at λ 1 =1.2619 is unstable and would slip spontaneously into its near neighbor stress-free mBCT phase with the local minimum energy of -4.2270eV. The initial BCC phase with the lowest energy of -4.280eV is the most stable in correspondence with the actual behavior of Fe. Furthermore, the stable region ranges from -79.7eV/nm 3 to 30.6eV/nm 3 in the theoretical strength or from 0.9064 to 1.1788 in the stretch λ 1 correspondingly.

Missing row reconstruction on three low index surfaces of ten FCC metals

“…The MEAM [25,26], which has been used successfully to study the (110) surface reconstruction in our previous papers [10,37], is applied again. The computer program compiled in Matlab language has been expanded to calculate the parameters for the ideal and (1×2) MR structure on two surfaces (x=(hkl)=(100) and (111)) of the FCC metals: the geometry factors…”

The structural response of BCC Fe lattice loaded in [110] direction

“…In the present paper, the MAEAM [30,31] which was used successfully to study the stability of BCC crystal Fe under [100] loading in our previous paper [22] is employed again. By substituting physical parameters of Fe [32]: the unstressed lattice constant a 0 , cohesion energy E c , mono-vacancy formation energy E 1f , and elastic constants C 11 , C 12 and C 44 , into Eqs.…”

“…In this paper, the theoretical strength and structural response of BCC Fe crystal under [110] uniaxial loading have been investigated with MAEAM. The MAEAM has been used successfully in our previous papers to analyze the stability of the face-centered cubic (FCC) crystal Ni [20], Cu [21], the BCC crystal Fe [22] and BCC transition metals [23] under uniaxial or hydrostatic loading and the other properties of the metals and alloys [24][25][26][27][28][29].…”