EI、Scopus 收录
中文核心期刊

铜基非晶合金热效应和剪切模量变化起源

ORIGIN OF HEAT EFFECTS AND SHEAR MODULUS CHANGES OF A Cu-BASED AMORPHOUS ALLOY

  • 摘要: 剪切模量在非晶合金黏性流动、扩散及结构弛豫等行为中起着重要作用. 宏观剪切弹性决定非晶合金热流变化.探索非晶合金在结构弛豫和玻璃转变过程中宏观力学性能与热流的关联有助于理解其力学行为起源. 本研究基于自间隙理论对Cu_49Hf_42Al_9非晶合金热流、剪切模量及黏度进行研究,建立剪切模量与热流之间的关联. 通过测量剪切模量精确测定自间隙缺陷浓度演化规律.从能量角度出发,通过激活能图谱探索自间隙缺陷浓度对非晶合金热力学性能的影响. 借助于动态力学分析仪研究非晶合金从室温到过冷液相区的动态弛豫行为,探索物理时效引起的结构弛豫以及内耗演化规律. 研究结果表明,自间隙理论可准确描述非晶合金的弛豫动力学、剪切软化及结构弛豫诱导的力学行为. 结合热流数据可以很好描述铸态和弛豫态非晶合金剪切模量随温度演化过程,激活能图谱直观表述了单位激活能可激活的自间隙缺陷浓度. 自间隙缺陷在结构弛豫中湮灭,表现为玻璃体系结构向更稳定状态迁移.在玻璃化转变过程中,缺陷浓度显著升高伴随热吸收,表现为原子大规模协同运动和剪切软化. 物理时效诱导非晶合金内耗和原子移动性降低. 过冷液相区内原子移动性高至消除了结构弛豫影响.

     

    Abstract: Shear modulus is one of important parameters to control the viscous flow, diffusion and structural relaxation of amorphous alloy. Macroscopic shear elasticity determines the change of heat flow. The correlation between the mechanical properties and the heat flow during the structural relaxation and glass transition is one of the important issues to understand the origin of mechanical properties of amorphous alloy. In the framework of the interstitialcy theory, the shear modulus, heat flow and viscosity of Cu_49Hf_42Al_9 amorphous alloy were used to probe the correlation between shear modulus and heat flow. In parallel, evolution of interstitialcy defects concentration was determined by shear modulus in initial and relaxed states. From the perspective of energy, the influence of interstitialcy defects concentration on the thermodynamic properties of amorphous alloy was investigated by activation energy spectrum (AES). Dynamic mechanical analysis (DMA) was used to investigate the dynamic mechanical process of the Cu_49Hf_42Al_9 amorphous alloy. Structural relaxation induced by physical aging and the evolution of internal friction in-situ annealing was discussed. The results demonstrated that interstitialcy theory could accurately describe the relaxation kinetics, shear softening and other phenomena induced by structural relaxation of amorphous alloy. Temperature dependence of the shear modulus in initial and relaxed states can be well predicted by the data of differential scanning calorimetry (DSC). Activation energy spectrum directly reflects the interstitialcy defects concentration, which can be activated per unit activation energy. Structural relaxation leads to a reduction of the defect concentration, which indicates the structure transforms to a more stable state. During the glass transition process, defect concentration rapidly increases, which corresponds to the shear softening accompanied by heat absorption. Structural relaxation induces decrease of both internal friction and atomic mobility of amorphous alloy. However, the atomic mobility is high enough to eliminate the influence of structural relaxation on defect concentration in the supercooled liquid region.

     

/

返回文章
返回