Influence of interface with mismatch dislocations on mechanical properties of Ti/Al nanolaminate

Abstract

As a representative boundary, interphase-interface may affect the strength or ductility of multilayered composites dramatically. However, the effect of the interface with mismatch dislocations on the mechanical behavior of multilayered composites is still not clear. In the present work, we performed molecular dynamics simulations to investigate the effect of interface structures and layer spacing on the mechanical properties of the Ti/Al nanolaminate. The results indicate that there are two transitions of the plastic deformation mechanism in the Ti layer with the increase of layer spacing in the sample with a coherent interface. The plastic deformation mechanism evolves from one that is dominated by dislocation to the phase transformation from the hcp-Ti to the fcc-Ti mode, which transfers to the dislocation slip deformation again. For the samples with an incoherent interface, the plastic deformation is dominated by the transformation from hcp-Ti to fcc-Ti, regardless of the variation of layer spacing, while the plastic deformations in the Al layers are mainly dislocations confined in the layer slip in the samples with both coherent and incoherent interfaces. When the layer spacing is larger than 6.6 nm, an obvious second hardening is observed due to the superior dislocation storage ability of the Ti/Al laminate with the incoherent interface. Meanwhile, extraordinary ductility is obtained when optimal layer spacing is employed in the Ti/Al laminate. Moreover, the phase transformation mechanism of hcp-Ti to bcc-Ti has also been explicated in the present work. The general conclusions derived from this work may provide a guideline for the design of high-performance Ti/Al multilayer and alloy devices.

Layer thickness dependent plastic deformation mechanism in Ti/TiCu dual-phase nano-laminates

“…The crystallography relation of HCP-Ti and BCC-Ti can be expressed as {0001} HCP ||{111} BCC and 1210 HCP || 110 BCC . The transformations of HCP-Ti and BCC-Ti have also been reported in both simulations [69] and experiment. [70]…”

Plastic deformation mechanism transition of Ti/Ni nanolaminate with pre-existing crack: Molecular dynamics study*

“…The most closed-packed planes of Ti (0001) and Ni (111) are stacked along the Z direction in all models, as the gaseous atoms prefer to deposit along those planes to gain the minimum energetic state during the preparation. [6][7][8][9] The interatomic potential is vital for the accuracy of the MD simulations, the embedded atomic method (EAM) potential [28,29] is utilized to predict atomic interaction for various atoms, which has been successfully used to describe the mechanical behaviors of nano-laminated materials of Ti/Al, [24] Cu/Au, [30] Cu/Ni, [31] and Cu/Ag. [32] During the simulation, Verlet integral algorithm is used to describe the motion of the newton atoms, and the time step is fixed at 3 fs (10 −15 s).…”

“…The interface can serve as a source and sink of these plastic deformation carriers, which promotes the ability to sustain the deformation of the material. [22][23][24] Figures 3(c)-3(f) show the microstructure evolutions of the crack-free Ti/Ni nanolaminate. The sample first yields at a strain of 0.098, which is defined as the yield point.…”

“…At the same time, the interaction between the interface and dislocation provides effective plastic deformation path to promote better plasticity. [21][22][23] However, most of the current studies focus on the FCC/FCC and FCC/BCC interfaces, while the study of HCP/FCC interface has been rarely reported except that by An et al [24] They performed MD simulations to evaluate the effects of coherent (transparent) and incoherent (opaque) interfaces on the tensile behaviors of Ti/Al (HCP/FCC) nanolaminates. The results demonstrated that plastic deformation mechanism varies with the interfacial structure.…”

Enhanced co-deformation of a heterogeneous nanolayered Cu/Ni composite

“…Many research studies show that nanolayered (NL) metallic composites possess outstanding mechanical and physical properties, [1][2][3][4][5][6][7][8] such as ultrahigh strength that approaches 1/2 or 1/3 of the theoretical limit, 9,10 due to their heterogeneous interfaces of high density. Existing investigations have been focused on the layer thickness (h) dependent strengthening mechanisms in the NL composites.…”