Abstract
The periodicity and density of atomic arrangement vary with the crystal orientation, which results in different deformation mechanisms and mechanical properties of γ-TiAl. In this paper, the anisotropic characteristics for γ-TiAl with (100), () and (111) surfaces during nanoindentation at 300 K have been investigated by molecular dynamics simulations. It is found that there is no obvious pop-in event in all load-depth curves when the initial plastic deformation of γ-TiAl samples occurs, because the dislocation nucleates before the first load-drop; while a peak appears in both the unloading curves of the () and (111) samples due to the release of energy. Stacking faults, twin boundaries and vacancies are formed in all samples; however, interstitials are formed in the (100) sample, a stacking fault tetrahedron is formed in the (111) sample; and two prismatic dislocation loops with different activities are formed in the () and (111) samples, respectively. It is also concluded that the values of the critical load, strain energy, hardness and elastic modulus for the (111) sample are the maximum, and for the (100) sample are the minimum. Furthermore, the orientation dependence of the elastic modulus is greater than the hardness and critical load.
Highlights
Micro–electromechanical systems (MEMS) have been successfully applied in fields such as biology or aerospace, which means that components of MEMS should be suitable for an increasingly complex working environment
The results indicate that the (100) sample the contact depth, h max is the maximum depth, ε is the correction factor, and ε = 0.75 for the spherical has the weakest resistance to plastic deformation, as the nanoindentation along the [100] orientation is indenter fittingto25–50%
The effect of crystal orientation on the deformation mechanisms and mechanical properties of γ-TiAl during nanoindentation at 300 K was demonstrated by molecular dynamics simulations
Summary
Micro–electromechanical systems (MEMS) have been successfully applied in fields such as biology or aerospace, which means that components of MEMS should be suitable for an increasingly complex working environment. Nanoindentation is an effective method to measure the mechanical properties of materials at the nanoscale, such as the elastic modulus, hardness and strain hardening effect. This technology has been applied to obtain the mechanical properties of various materials including pure metals such as Al, Cu, Ag, Ni, and Fe [5,6,7,8]; and alloys such as TiAl, U–Cu, Fe–Ni–C, Zr–Cu–Ag–Al and nickel superalloys [9,10,11,12,13,14,15]. The defect evolution, load-depth curve, hardness, elastic modulus, critical load and strain energy for different samples are analyzed in detail
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