Study On Crystallization,wear And Creep Behaviors Of High Entropy Bulk Metallic Glasses

High-entropy metallic glass combines the characteristics of two kinds of advanced metal materials:metallic glass and high-entropy alloy.Consequently,it is expected as a next-generation material in aerospace engineering,microelectromechanical systems,and various other applications.However,the developmental course of this material has been short,and research on this material has been both scarce and superficial.The present study contrasts the behaviors of Ti Zr Hf Be Cu(Ni)high-entropy bulk metallic glass(HE–BMG)and classical Zr-based bulk metallic glass(BMG)vit-1.The study focuses on the phenomena that affect the serviceability of the material,such as crystallization,wear,and creep behaviors.The main research contents and conclusions are summarized below.The isothermal and non-isothermal crystallization kinetics of Ti₂₀Zr₂₀Hf₂₀Be₂₀Cu_20-xNi_x(x=0,10,20)HE–BMGs were studied by differential scanning calorimetry(DSC).Complex multi-step crystallization behavior was observed under continuous heating conditions.Increasing the Ni content increased the glass transition temperature and narrowed the supercooled liquid region.The Ni addition also enhanced the activation energy of the first crystallization peak of the Ti Zr Hf Be Cu alloy and promoted the precipitation of more kinds of crystalline phases in the crystallization process.Accordingly,the crystallization process became more difficult,resulting in a better glass-forming ability.Next,the crystallization mechanism of Ti₂₀Zr₂₀Hf₂₀Be₂₀Cu_20-xNi_x(x=0,10,20)HE–BMG was deduced from the Avrami exponents.The crystallization processes of all three HE–BMGs were dominated by three dimensional diffusion-controlled growth.The high-entropy effect on the crystallization process became more significant with increasing Ni content.Next,the nano-scratching behaviors of Ti₂₀Zr₂₀Hf₂₀Be₂₀Cu_20-xNi_x(x=0,10,20)HE–BMGs and vit-1 BMG were observed at different scratch rates.The scratch rate exerted no obvious effect on the nanoscratch behaviors of the HE–BMGs or vit-1 BMG.HE–BMGs achieved higher wear resistance than vit-1 BMG.The hardness values and wear resistances of the HE–BMGs were enhanced owing to the high entropy of these materials,which encouraged an atomically compact stacking structure.The creep resistance of Ti Zr Hf Be Cu HE–BMG at room temperature was further improved by partially replacing Cu with Ni.The material flow and deformation mechanisms during scratching were determined from the change of friction coefficient.The added Ni was found to change the material-removal mechanism.Finally,the creep properties of Ti Zr Hf Be(Ni)HE–BMGs and vit-1 BMG at room temperature were studied by nano-indentation.The creep curves of the studied alloys at room temperature were fitted to the Kelvin model,and the strain rate sensitivities,creep compliance spectra,and creep retardation spectra were also analyzed.HE–BMGs exhibited better creep resistance than traditional single principal component BMG,revealing that their high entropy influenced the creep resistance at room temperature.The room-temperature creep resistance of Ti Zr Hf Be Cu HE–BMG was significantly enhanced by partially replacing Cu with Ni,which attributes to the increase of mixing entropy and the Young's modulus induced by Ni addition.