Study On Dynamic Properties Of Cu-Based Alloy During Glass Transition

At present,amorphous alloys are widely used in various fields,mainly because of their more excellent and unique properties.However,due to the lack of experimental conditions,it is difficult to effectively control the properties of amorphous alloys,which hinders the progress of basic application research and industrial technology of amorphous alloys.In this paper,the effects of temperature and composition on the dynamic properties of Cu-based alloy during glass transition have been studied by means of molecular dynamics simulation technique.Firstly,the effect of temperatures on the dynamic properties of Cu glass transition was studied.From the mean square displacement curve,it is found that the lower the temperature of the system is,the greater the limit of atomic motion is,the more obvious the platform region is,and the stronger the dynamic heterogeneity of the system is.It is found from the diffusion coefficient curve that the lower the temperature is,the smaller the diffusion coefficient is,and that the diffusion coefficient and temperature in the high temperatures stage satisfy the Arrhenius equation.It is found from the non-Gaussian parameter that the peak values of the non-Gaussian parameter increases gradually with the decrease of temperatures,and moves to a longer relaxation time region,indicating that there is dynamic heterogeneity in the system,and the degree of such heterogeneity with temperatures.The degree decreased and gradually strengthened.At the same time,it is found that the variation of non-Gaussian parameter with time accords with power-law function in?relaxation,and the relationship between the peak values of non-Gaussian parameter and?relaxation time and temperatures conforms to Arrhenius equation.Then through the relationship between the atomic displacement distribution and the temperatures,it is concluded that the lower the temperature is,the smaller the mobility of the atom is,and the larger the binding of the atomic motion is,the more concentrated the range of the moving displacement distribution is,but when the temperature of the system is higher,the lower the temperature,the smaller the mobility of the atom.At the same time,it is found that the maximum frequency of atomic displacement distribution satisfies the Arrhenius equation with the change of temperatures,while the maximum frequency corresponds to the maximum frequency.The change of displacement with temperature is linear.Then,the effect of composition change on the dynamic properties of Cu-Zr,Cu-Zr-Al alloy was studied.It was found that the diffusion coefficient of Cu-Zr,Cu-Zr-Al alloy obeyed the Arrhenius equation at high temperature.With the decrease of temperatures,the diffusion law gradually deviates from the Arrhenius equation.At the same time,it was found that the change of composition in Cu-Zr,Cu-Zr-Al alloy had little effect on diffusion coefficient,and the more Cu content in Cu-Zr alloy,the smaller the diffusion activation energy was,and the more Al content in Cu-Zr-Al alloy was,the greater diffusion activation energy was.By studying the non-Gaussian parameter,it is found that the non-Gaussian parameter of Cu-Zr,Cu-Zr-Al alloy satisfies the power law function at?relaxation stage and time,and the variation of non-Gaussian parameter peak value with temperature at low temperature conforms to the Arrhenius equation.However,it deviates from the Arrhenius equation at high temperature,in which the parameter values in the power law function and the Arrhenius equation are close to each other.The results show that the composition change of Cu-Zr,Cu-Zr-Al alloy system has little effect on the kinetic properties.Finally,the effects of element addition on diffusion coefficient and the peak value of non-Gaussian parameter?_maxax was further analyzed for three kinds of amorphous alloy systems of Cu,Cu-Zr,Cu-Zr-Al.It was found that with the increase of element types in the alloy system,the temperature of its diffusion coefficient?the temperature corresponding to the diffusion coefficient deviating from the Arrhenius equation?is getting larger and larger.At the same time,the peak value of non-Gaussian parameter?_maxax of Cu-Zr-Al amorphous alloy is the largest,so that Cu-Zr-Al has strong dynamic heterogeneity.The results show that the more kinds of elements in the alloy,the stronger the complexity of the alloy,and the stronger the dynamic heterogeneity of the amorphous alloy formed.