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

Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials,but the underlying deformation mechanism is still under the way of exploring.Here,the mechanical properties and plastic deformation mechanism of Ti/TiCu dual-phase nanolaminates(DPNLs)with different layer thicknesses are investigated using molecular dynamics simulations.The results indicate that the influence of the layer thickness on the plastic deformation mechanism in crystalline layer is negligible,while it affects the plastic deformation mechanism of amorphous layers distinctly.The crystallization of amorphous TiCu is exhibited in amorphous parts of the Ti/TiCu DPNLs,which is inversely proportional to the layer thickness.It is observed that the crystallization of the amorphous TiCu is a process driven by stress and heat.Young's moduli for the Ti/TiCu DPNLs are higher than those of composite material due to the amorphous/crystalline interfaces.Furthermore,the main plastic deformation mechanism in crystalline part:grain reorientation,transformation from hexagonal-close-packed-Ti to face-centered cubic-Ti and body-centered cubic-Ti,has also been displayed in the present work.The results may provide a guideline for design of high-performance Ti and its alloy.

Anisotropic plasticity of nanocrystalline Ti:A molecular dynamics simulation

Using molecular dynamics simulations,the plastic deformation behavior of nanocrytalline Ti has been investigated under tension and compression normal to the{0001},{1010},and{1210}planes.The results indicate that the plastic deformation strongly depends on crystal orientation and loading directions.Under tension normal to basal plane,the deformation mechanism is mainly the grain reorientation and the subsequent deformation twinning.Under compression,the transformation of hexagonal-close packed(HCP)-Ti to face-centered cubic(FCC)-Ti dominates the deformation.When loading is normal to the prismatic planes(both{1010}and{1210}),the deformation mechanism is primarily the phase transformation among HCP,body-centered cubic(BCC),and FCC structures,regardless of loading mode.The orientation relations(OR)of{0001}HCP||{111}FCC and<1210>HCP||<110>FCC,and{1010}HCP||{110}FCC and<0001>HCP||<010>FCC between the HCP and FCC phases have been observed in the present work.For the transformation of HCP→BCC→HCP,the OR is{0001}α1||{110}β||{1010}α2(HCP phase before the critical strain is defined as α1-Ti,BCC phase is defined as β-Ti,and the HCP phase after the critical strain is defined as α2-Ti).Energy evolution during the various loading processes further shows the plastic anisotropy of nanocrystalline Ti is determined by the stacking order of the atoms.The results in the present work will promote the in-depth study of the plastic deformation mechanism of HCP materials.

基于分子动力学模拟的铜锆晶体/非晶双相纳米复合材料力学行为

金属玻璃因其较差的室温塑性限制了其广泛应用,因此提升金属玻璃的力学性能、探明金属玻璃的变形机制已经成为当前材料领域的研究热点。采用分子动力学方法研究了晶粒尺寸和分布对晶体/非晶B2-CuZr/CuZr双相复合材料力学行为的影响。研究结果表明,随着纳米晶粒的尺寸增大,复合材料变形模式发生了从相对均匀变形到单一剪切带的局部变形的转变。研究指出,增大纳米晶粒尺寸/体积分数能有效提高复合材料的峰值应力,但除了较小尺寸纳米晶粒模型外,双相复合材料的塑性没有明显增强。此外,相对于交叉排列,纳米晶粒的对齐排列导致了更严重的塑性应变局部化。本文的研究结果对于设计和制备高性能的金属玻璃材料具有重要的参考价值和指导意义。