Computer simulation of dislocation cores in B2 NiAl intermetallics

Abstract

Using embedded atom method and molecular static relaxation method, the core structure of 〈100〉, 〈110〉 edge dislocations, 〈100〉 screw dislocation, the interaction between point defects and 〈100〉 edge dislocation in NiAl intermetallics were investigated. The results show that 〈100〉 edge dislocation expands along [110] and

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orientation on the (001) slip plane. The core structure of 〈100〉 edge dislocation on (001) plane is like a ”butterfly”, while it is very compact when it lies on {110} slip plane. So NiAl will have a 〈100〉 {110} slip system in stead of 〈100〉 {100} slip system, as experiments showed. 〈110〉 edge dislocation has a more expanded core structure and the atoms of dislocation core distort more heavily. None dislocation dissociation was found in the studied dislocations. The outlines of dislocation core structures change very little after a row of point defects are introduced in them, which can be explained by point defects’ little effects on the stress field around dislocation core. The results also show that it is hard to change dislocation core structure by decreasing alloy order using the method of introducing limited point defects into the alloy.

Keywords

dislocation core structure / NiAl / computer simulation / point defects

References

[1] MillsM J, MirocleD B. The structure of a 〈100〉 and a 〈110〉 dislocation cores in NiAl. Acta Metall Mater, 1993, 41: 85-95

[2] NagpalP, BakerI. TEM in-situ straining of NiAl. Intermetallics, 1994, 2: 23-28

[3] MiracleD B, RussellS, LawC C. Slip system modification in NiAl. High Temperature Ordered Intermetallic Alloys V, 1995, 364: 225-229

[4] CrimpM A, TonnDC, ZhangY. Dislocation core structures in B2 NiAl alloys. Materials Science and Engineering, 1993, A170: 95-102

[5] MillsM J, DawM S, FoilesS M, et al.. HRTEM observation and EAM calculation of dislocation cores in NiAl. High Temperature Ordered Intermetallic Alloys V, 1993, 288: 257-261

[6] VailheC, FarkasD. Trends in dislocation core structures and mechanical behavior in B2 aluminides. High Temperature Ordered Intermetallic Alloys VI, 1995, 364: 389-392

[7] FoilesS M, BaskesM I, DawM S. Embedded-atom-method functions for the fcc metals Cu, Ag, Au, Ni, Pd, Pt, and their alloys. Physical Review B, 1986, 33: 7983-7989

[8] DawM S, BaskesM I. Embedded-atom-method: Derivation and application to impurities, surfaces, and other defects in metals. Physical Review B, 1984, 29: 6443-6452

[9] LiuZhenyun, LinDongliang, ChenDa. Atomistic simulation of point defects in NiAl alloy. Trans Nonferrous Met Soc China, 1997, 7(2): 128-131

[10] LiuZhenyun, LinDongliang, HuangBaiyun. Simulation of grain boundary in NiAl alloy. Trans Nonferrous Met Soc China, 1999, 9(1): 105-105

[11] VitekV. Structure of dislocation cores in metallic materials and its impact on their plastic behavior. Progress in Materials Science, 1992, 36: 1-14

[12] NoebeR D, BowmanR R, NathalM V. Physical and mechanical properties of the B2 compound NiAl. International Materials Reviews, 1993, 38: 193-234