Investigation On The Relationship Between Hardness,elastic Modulus And Tribological Properties Of Pd-W-Si Alloys Prepared By High Throughput Method

As a new type of film material developed in recent years,amorphous alloy(also known as metallic glass)film not only inherits the excellent properties of high strength,high hardness,and high wear resistance endowed by the microstructure of bulk amorphous alloy with long-range disorder and short-range order,but also overcomes the intrinsic brittleness of bulk amorphous alloy.It has been widely used in wear-resistant fields such as blade coating and biological appliance coating.The friction and wear properties of amorphous alloys are usually closely related to their physical properties.The hardness(H)has long been considered as the main factor determining the wear resistance of coating materials.The elastic modulus(E)also affects the wear resistance of materials.The H/E value can effectively reflect the wear tribological properties of materials.However,the inconsistency of amorphous alloy preparation methods and alloy elements could affect the accuracy of experimental phenomena and the reliability of conclusions.The mechanism of the influence of hardness and elastic modulus on the tribological properties of amorphous alloys is yet of necessity to be explored.Therefore,based on high-throughput magnetron co-sputtering,a ternary alloy library containing different components of Pd-W-Si was prepared in this paper.Nano-indentation and nano-scratch experiments were used to compare amorphous and crystalline materials and explore the relationship between indentation hardness(H),elastic modulus(E)and the nanoscale tribological properties of this alloy system.The study found that in the Pd-W-Si ternary alloy material library:(1)Although the scratch depth(h_s)follows a decreasing trend with increasing hardness and elastic modulus,the matching degree of data points with the trend line is stronger for elastic modulus as compared with hardness,which can be rationalized by the volume of shear transformation zone(STZ)that suggests the more difficult activation of the deformed unit in amorphous structure and thus the better scratching resistance:for the alloy with large H and E,the STZ volume is estimated to be small,resulting in a shallow scratch depth and high scratch resistance,while the fluctuation of STZ volume with E is weaker than H.(2)The correlation of elastic recovery(η)is weak with hardness but strong with H/E.In particular,the elastic recovery increases with H/E.This is because,for the alloy with high H/E,the energy absorbed in an elastically deformed regime is more and the material after elastic-plastic deformation is easier to recover;the phenomenon that the pile-up height of amorphous alloy decreases with H/E also promotes the free slipping of shear bands to a certain extent,thus leading to higher elastic recovery and better wear resistance.(3)Under the same load,the tribological properties of the amorphous alloy are better than those of the corresponding crystalline alloy as a whole,which reflects the different deformation mechanisms of the two alloys:dislocation of the crystalline alloy is the basic carrier of plastic deformation;STZ of amorphous alloy is the basic carrier of plastic deformation.(4)Based on the high-throughput database in the amorphous and crystalline alloy systems,an empirical exponential law correlation(where E_r is the reduced modulus corresponding to E)between the unloading curve exponent m and E_r/H has been found,which optimizes the nonlinear relationship between H/E_r and W_e/W_tempirical model.The limitation of the original theoretical model has been overcome through the verification of a large number of experimental data.