Hf元素添加对CuZr基非晶合金动态弛豫的影响

EFFECT OF Hf ELEMENT ADDITION ON DYNAMIC RELAXATION PROCESS OF CuZr-BASED AMORPHOUS ALLOY

考虑到非晶合金具有独特的无序微观结构,其表现出极为复杂的弛豫动力学特性.动态弛豫行为在非晶合金中普遍存在,深刻理解其机制对于解构非晶合金固有的非均匀微观结构至关重要.少量元素的添加是调控非晶合金微观结构有效手段之一.本研究以玻璃形成能力良好的Cu_(46)Zr_(47-x)Hf_(x)Al_(7)(x=0,8)非晶合金为模型合金,运用动态力学分析方法研究复模量随频率和温度的变化,进而探究Hf元素取代Zr元素对动态弛豫的影响.在动态力学频率谱中,借助准点缺陷理论阐明非晶合金在玻璃转变温度T_(g)以下处于等构型状态,准点缺陷浓度保持恒定;而在T_(g)以上,准点缺陷浓度随温度的上升呈线性增加.Hf元素的添加会降低玻璃体系等构型状态下的准点缺陷浓度,并抑制原子迁移能力.通过获取连续和离散的弛豫时间分布,直观展示了非晶合金的动力学非均匀性特征.在动态力学温度谱中,Hf元素的引入增加了玻璃体系的混合焓,抑制了β弛豫强度.进一步从内耗角度表明,Hf元素的引入不仅提高了与β弛豫相关的基本结构单元的激活难度,还增加了整个β弛豫过程的激活能.

Amorphous alloys,owing to their distinctive disordered microstructure,display intricate relaxation dynamics.Dynamic relaxation behavior is prevalent in amorphous alloys,and a deep understanding of its mechanism is essential for deconstructing the inherent micro structural heterogeneity of amorphous alloys.The addition of minor elements is one of the effective means to regulate the microstructure of amorphous alloys.In this study,the Cu_(46)Zr_(47x)Hf_xAl_7(x=0,8)amorphous alloys,known for their excellent glass-forming ability,were used as model alloys.Utilizing dynamic mechanical analysis methods,the study investigated the variation of complex modulus concerning frequency and temperature,thereby exploring the impact of substituting Hf for Zr on dynamic relaxation.In the frequency spectrum of dynamic relaxation,the application of quasi-point defect theory elucidated that amorphous alloys exist in an isoconfigurational state below the glass transition temperature(T_g),maintaining a constant concentration of quasi-point defects.Whereas,above T_g,the concentration of quasi-point defects increases linearly with the increase of temperature.The addition of Hf decreases the concentration of quasi-point defects in the iso-configurational state of glass system and suppresses atomic migration ability.Through continuous and discrete relaxation time distributions,it visually demonstrates the characteristics of dynamical heterogeneity of amorphous alloys.Regarding the temperature spectrum of dynamic relaxation,the introduction of Hf increases the mixed enthalpy of the glass system and suppresses the strength ofβrelaxation.Further analysis from an internal friction perspective indicates that the introduction of Hf not only elevates the activation difficulty of basic structural units related toβrelaxation but also increases the activation energy of the entireβrelaxation process.