Dynamic mechanical relaxation and thermal creep of high-entropy La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10)bulk metallic glass

Dynamic mechanical relaxation is a fundamental tool to understand the mechanical and physical properties of viscoelastic materials like glasses.Mechanical spectroscopy shows that the high-entropy bulk metallic glass(La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10))exhibits a distinctβ-relaxation feature.In the present research,dynamic mechanical analysis and thermal creep were performed using this bulk metallic glass material at a temperature domain around theβrelaxation.The components of total strain,including ideal elastic strain,anelastic strain,and viscous-plastic strain,were analyzed based on the model of shear transformation zones(STZs).The stochastic activation of STZ contributes to the anelastic strain.When the temperature or external stress is high enough or the timescale is long enough,the interaction between STZs induces viscous-plastic strain.When all the spectrum of STZs is activated,the quasi-steady-state creep is achieved.

Slowβrelaxation in La-based metallic glasses based on mechanical spectroscopy measurements

Dynamic mechanical relaxations of La-based metallic glasses were investigated by mechanical spectroscopy.In the framework of the mixing enthalpy of constituent atoms,it was found thatβrelaxation was less evident by the addition of Cu to replace Ni in the LaCuNiAl glassy alloy.By introducing Cu into the LaNiAl metallic glass,the mixing enthalpy was less negative,which led to weakerβrelaxation of the metallic glasses.Theαrelaxation of the La-based metallic glasses could be described by a Kohlrausch-Williams-Watts（KWW）function with a Kohlrausch exponentβKWW around 0.5.It should be noted that physical aging above the glass transition temperature Tginduced a decrease ofβrelaxation intensity in the La-based metallic glass.