Study On Mechanical Properties Of Metallic Glass Structures With Negative Poisson’s Ratio

Metallic glasses（MGs）have excellent mechanical,magnetic and chemical properties.Auxetic materials have broad application prospects due to their unique expanding laterally when stretched,however,bulk MGs could not show auxeticity because of their intrinsic isotropic nature.Here we construct chiral Cu₅₀Zr₅₀metallic glass nanolattices（CMGNs）with cavities and corner fillets and investigate their auxeticity and underlying mechanism with molecular dynamics simulations.The effect of geometric parameters on density,Young’s modulus,Poisson’s ratio and atomic shear strain of CMGNs was discussed in detail.The mechanism and principle of the auxeticity were explored,and the correlation between strain and Poisson’s ratio was determined.Our study reveals the mechanism of auxeticity in CMGNs and provides a feasible method to optimize auxetic performance and its density by structure designing of MGs.The research work mainly includes the following aspects:（1）The effects of the cavity radii on the mechanical properties of the Cu₅₀Zr₅₀CMGNs were studied.it was found that all CMGNs show improved auxeticity and reduced density compared to bulk MGs.For CMGNs with cavities,negative Poisson’s ratio and ultimate tensile strength（UTS）increase first and then decrease with increasing cavity radius,with the cavity radius of 2.5 nm being the most favorable for auxeticity and enhanced UTS.The auxetic mechanism is attributed to the competition between rotation behavior in central nodes and non-affine deformation under tension.（2）The effects of corner fillets on the mechanical properties of Cu₅₀Zr₅₀ CMGNs were studied.Corner fillets structure significantly improves Young’s modulus of CMGNs,resulting in a reduced elastoplastic phase as well as weakened plasticity during tension process;the cavity radii have a great influence on its mechanical properties.During the gradual increase of the cavity radii,the auxeticity of samples disappears when the cavity radius increases to 5.0 nm in this study（other parameters are fixed）.Corner fillets can undermine the rotation deformation mechanism of CMGNs,resulting in weakened auxeticity.（3）The mechanical properties of CMGNs by laser 3D printed and traditional cast were compared.Multi-channel scanning and cross-layer scanning can reduce both temperature gradient and residual stress,resulting in high density and strength.Compared to as-cast CMGNs,it is easier for laser 3D printed ones to form a preferred orientation.Due to its very high cooling rate,laser 3D printed CMGNs possess low density and high Young’s modulus.