Study On The Effect Of Surface Mechanical Attrition Treatment On The Structure,Mechanical Properties,and Corrosion Behavior Of A Zirconium-based Amorphous Alloy

Metallic glasses,also known as amorphous alloys,are glassy alloys solid formed by the deep undercooling of high temperature melt up to the glass transition temperature and the structure is suddenly"frozen".With their unique structure and excellent properties,amorphous alloys have become a hot topic in the field of condensed matter physics and materials science since they were discovered,especially the study of the relationship between structure and performance,which is great useful for understanding the nature of amorphous alloys and improving their engineering applications.For this purpose,this paper selects Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅(at.%)zirconium-based amorphous alloy as the research material,and use surface mechanical attrition treatment(SMAT)to modify its surface,and systematically study the effects of SMAT for different time on the structure,mechanical properties,crystallization behavior and corrosion resistance.The main content is as follows:The relationship between structural changes and mechanical properties was studied.X-ray diffractometer,differential scanning calorimeter,transmission electron microscope and hardness test results show that with the increase of SMAT time,the content of nano-scale local crystal-like-order structure increases,the relaxation enthalpy decreases,and the free volume decreases,resulting in increased hardness.The three-point bending fracture experiment showed that the amorphous alloy after SMAT has more shear bands at the front end of the notch,and the plastic deformation zone at the front of the notch is obvious,and the fracture toughness is improved.The fracture toughness of the sample treated by SMAT for 30 minutes is the largest,which is the result of the combined effect of residual compressive stress and structural inhomogeneity.The relationship between structure change and crystallization kinetics was studied.In the TEM in-situ heating process,the structure evolution process of the amorphous alloy after SMAT during the heat preservation and annealing process in the cold liquid interval was systematically studied.In the phase separation stage,a metastable amorphous or semi-crystalline phase with a size of 2?6 nm is formed.When the temperature rises to 773 K,the area fraction of the crystal-like-order structure increases with the increase of the SMAT time,which is caused by the initial crystal-like-order structure inside the sample.With the extension of the holding time at 773 K,the metastable state will trigger“avalanche-like”nucleation,the crystalline phase will precipitate out quickly and the metastable quasicrystalline phase will be transformed into a more stable crystalline phase.After holding for the same time,the area fraction of crystal particles produced by the amorphous alloy material after SMAT increases faster than that of the as-cast material.The relationship between structural changes and corrosion resistance was studied.Research on the corrosion behavior of zirconium-based amorphous alloy materials after SMAT in 3.5 wt.%NaCl solution found that SMAT has an important effect on improving the corrosion behavior of amorphous alloy materials.The amorphous alloy material after SMAT has a lower corrosion current density and a higher self-corrosion potential than the as-cast amorphous alloy,and the pitting pits are reduced,and the depth becomes shallower.XPS test analysis shows that a large number of oxides of Zr,Cu,Ti and Al are formed on the surface of the material after corrosion.The surface nano-layer of the amorphous alloy material after SMAT is more dense,which significantly improves the corrosion resistance of the material.The microstructure of the sample after 60 minutes SMAT is the most uniform,thus exhibiting the most excellent corrosion resistance.