Study On The Correlation Between Microstructure And Glass Forming Ability Of CuZr Allo

The article summarizes the background of the topic selection,the development and application of amorphous alloys,and introduces the microstructure of amorphous alloys,the research progress of glass-forming ability of CuZr alloys,molecular dynamics simulation,characterization and analysis of microstructure of amorphous alloys.As a result of the low cost,abundant experimental research,and relatively strong glass-forming ability,CuZr alloy is the focus of theoretical research.Based on molecular dynamics,to select the appropriate potential function,the rapid solidification process of CuZr alloy is simulated.Simulation results are analyzed by energy curve,pair distribution function（PDF）,the Largest Standard Cluster Analysis（La SCA）,topologically close-packed（TCP）structure and 3D visualization.The rapid solidification of Cu₆₄Zr₃₆ nanodroplets of different sizes at 10¹² K/s was simulated by molecular dynamics.The results show that Cu₆₄Zr₃₆ nano-droplet gradually solidified into amorphous nanoparticles,and the short-range order characteristic length（average cut-off radius a R_c）output by La SCA can effectively distinguish the physical state change（liquid-solid phase transition）of the metal system during the solidification process.The solidification process of Cu₆₄Zr₃₆nanodroplets undergoes four stages:high temperature melt,liquid-liquid phase transition(initial temperature is T_ll),liquid-solid phase transition(initial temperature is T_ls,end temperature is T_e（T_g）)and amorphous solid.The parameter changes based on TCP structure can effectively characterize the details of the structural evolution during the phase transition process,and it is found that the solidification process of nanodroplets includes four stages:embryo,aggregation,growth and coarsening.In the liquid-liquid phase transition interval,the TCP atoms increase rapidly,and the maximum size of the TCP clusters begins to increase;the liquid-solid phase transition interval is the key stage when the TCP clusters are connected to each other to form larger clusters.The number of TCP atoms and critical temperatures(T_ll,T_ls,and T_e（T_g）)change with the size of nanoparticles in a consistent way,while Z12（icosahedral）atoms did not have such a correspondence.Simulate the rapid solidification process of multi-component CuZr binary alloy system（the percentage of Cu is 48～69%,a total of 25 components）at a cooling rate of10¹² K/s,and analyze its microstructural characteristics and variation of microstructure with composition.The results show that the partial PDF curve based on the element-type atom pairs in the alloy is difficult to explain the central position of the first peak of the total PDF and the splitting phenomenon of the second peak;the partial PDF curve analysis based on Z12 atoms is also difficult to explain,but the partial PDF curve based on TCP atoms can reasonably explain the splitting of these two peaks.Therefore,the topologically close-packed（TCP）structure is the basic structural feature of the CuZr amorphous alloy system.The width at half of the first peak on the PDF curve,the number of short-range order CNSs,and the number of the main four medium-range order structures are all difficult to explain the variation of amorphous phase density with composition in CuZr alloy.The number of TCP atoms increases with the increase of Cu content,and local maxima are obtained near the Cu content of 50.6%,56.6%and 63.1%,which is consistent with the variation of amorphous phase density with Cu content.Most of the TCP La SC are connected to each other through point-shared（PS）,edge-shared（ES）,surface-shared（FS）and volume-shared（VS）to form medium and long-range structure.And the number of them with the composition is also the same as the variation of the density of the amorphous phase with the Cu content.It is this tight connection that makes the amorphous structure more stable.In conclusion,the TCP structure is a structural feature of CuZr alloys,which can reasonably explain the variation of amorphous phase density with Cu content.This study establishes a correlation between the microstructure and the glass-forming ability of amorphous alloys.