A Theoretical Study About The Stacking Fault And Anti-phase Boundary In FCC Metals And Alloys

The plane defects of metals and alloys include grain boundary, sub-grain boundary, twins grain boundary, phase boundary, stacking fault, outward surface, etc. plane defects have important impacts on the physical, chemical and mechanical properties of metals and alloys as well as point and line defects (dislocation). Stacking fault energy plays an important role in the decompounds of dislocation and the martensitic transformation behavior of shape mechanism as forming nucleus with stacking fault. And anti-phase boundary energy is an important factor in a alloy material's resistance to deformation, and also affects the way deformation occurs. Therefore, a systemic study of the structure and energy of stacking fault and anti-phase boundary of FCC metals and alloys will provide theoretical foundation and introduction for the mastery and transforming of material properties and designing new materials. In this paper, we have made a theoretical study about the structure and energy of stacking fault and anti-phase boundary of metals and alloys by using the embedded atom method (EAM).(1)The Stacking Fault Energies (SFE) of FCC metals have been calculated by the embedded-atom method (EAM) for 10 FCC metals Cu, Ag, Au, Ni, Al, Rh, Ir, Pd, Pt and Pb. The calculated values are in good agreement with experimental results excepting Rh and Ir. At the same time, we obtained that the energy of twins grain boundary (without lattice relaxation) equals a half of the single intrinsic stacking fault energy.(2) The multilayer relaxation of FCC metals Cu, Ag, Al and Pb , which are resulted by the Stacking Fault have been calculated by using the modified atom-embedded analysis method (MAEAM), and have calculated their Stacking Fault Energies. The result show that, the model of lattice relaxations resulted by stacking fault are alike each other in these 4 metals. That is the 4 {111} plane's space would be expanding, and other plane's space would be reducing differently. The lattice relaxation's effect in calculation of stacking fault energy are different follow metal. So when we calculate the stacking fault energies we couldn't neglect the effect by lattice relaxation arbitrarily.(3) The alloy stacking fault energy of four solid solution alloy A1-Nk Cu-Ag> Pb-Ag> Cu-Pb in all compositions have been calculated by using the modified analytical embedded atom method (MAEAM). And the stacking fault energy of Lh inter-metallic compound N13AI was calculated to be 16.43 mJ/m2. Comparing the calculated result of alloy stacking fault energy of M3AI with and other theoretical values, it can be found that our calculated result is more close to the experimental results than other theoretical values.(4) With modified analytical embedded atom method (MAEAM), the anti-phase boundary energies (APBE) of three possible crystal planes {001}, {011} and {111} in intermetallic compound Lh type NisAl have been calculated to be 61.77, 78.22 and 132.5(mJ/m2) respectively. From energy minimization, in the process of disorder-order phase transformation in intermetallic compound Ni3Al, the favorable boundary should be {001}, {011} and {111} successively, while the temperature is falling across the courier point (TC=1395°C).(5) With modified analytical embedded atom method (MAEAM), in intermetallic compound DO3 -type FesAl, the energies of two kinds of anti-phase boundaries in crystal planes {110} and {211} have been calculated to be 85.23, 90.16, 87.54 and 96.87 (mJ/m2) respectively. These anti-phase boundary are distinguished by the fault displacement R =< 111 > a 14 or R =< 111 > a 12, where a is the lattice constant of the DO3 structure.