| As a new member of the material family,metallic glass has a short-range ordered long-range disordered glass-like structure.The particular structure makes metallic glass have benign properties that high yield strength,excellent corrosion resistance,well biocompatibility attracted extensive attention of scholars.Whereas,because metallic glass does not have defects similar to the grain boundaries in crystalline materials,there is no resist mechanism for deformation,so show brittle,which severely limits the applications of metallic glass.It cannot adjust the properties of metallic glass by changing the structure because of the lack of defective structures.In response to this challenge,Professor Gleiter from Germany proposed the concept of Nano-metallic glass（Nanoglass）,which introduced interfaces in glass.It provided the possibility to adjust the mechanical properties of metallic glass.This article uses DC magnetron sputtering method to prepare Cu50Zr50 Nano-metallic glass（NMG）under a pressure of 0.5 Pa.Nano-indentation test results show that the hardness of the Nano-pillar in the thickness direction is greater than the horizontal direction.Further,we carried out the compression test of the micro column,and found that the yield strength in the thickness direction of NMG was higher than its horizontal direction.Using scanning electron microscopy to observe the crack distribution of the micro-pillars after compression,it show the micro-pillars in the thickness direction are plastically deformed in a disperse form,while the micro-pillars in the horizontal direction are deformed in a step-like form.In order to explain the cause of the anisotropy of NMG,we found that there are Nano-pillars of two sizes growing in the thickness direction,with the diameters are～10 nm and～110 nm,and the atomic arrangement of the interface is relatively Loose relative to the Nano-pillars,and the interface thickness be ween the large Nano-pillars is great,and the atom arrangement is more relax.We conduct Nano-scale mechanical property tests on the surface of NMG using the AMFM module of the atomic microscope.The results show this heterogeneous Nano-pillar structure makes the Young’s modulus of the interface smaller than the Nano-pillars,and the difference in mechanical properties between large interfaces and Nano-pillars is greater than between small interfaces and Nano-pillars,so that the shear band is produced from the large interface under pressure,resulting in the thickness and horizontal anisotropy of NMG.In order to control the structure of NMG,the magnetron sputtering pressure was reduced to0.1 Pa,make the large-sized Nano-pillars were eliminated.The anisotropy leading to hardness and yield strength tends to weaken.And the disappearance of the large interface induces the production of multiple shear bands,so that the micro-column of NMG still go by about 15%plastic deformation after the yield point,making it have better compression plasticity.Regulating pressure to 1 Pa,make the diameter of large-scale Nano-pillars decreases,and the anisotropy of hardness and yield strength in different directions of the NMG increases.On the other hand,the power of the control,Scanning electron microscope,Nano-indentation,and AMFM module test results show that the add in power increases the diameter of the Nano-pillars,the Young’s modulus and hardness of NMG,and the large interface has the smallest Young’s modulus.Using molecular dynamics emulation of micron-column compression experiments,the upshot show that the thickness direction does have a higher yield strength at 0.5 Pa.Analyzing the strain distribution of the micron column under pressure,the shear transition zone in the thickness direction is more uniform.The shear transition region in the horizontal direction is concentrated at the interface,which causes the Nano-metal glass film to be anisotropic.And the decrease of the Nano-pillar diameter leads to an augment in the yield strength in the horizontal direction,a decrease in the yield strength in the thickness direction,and an augment in the anisotropy of the yield strength in different directions,which is consistent with the experimental content.In short,the asymmetry columnar structure of NMG results in its anisotropy in thickness and horizontal direction,and changing its structure can regulate the anisotropic trend of NMG. |
