金屬玻璃的屈服應(yīng)力和彈性應(yīng)變極限遠(yuǎn)遠(yuǎn)超過傳統(tǒng)的多晶合金,但具有應(yīng)變軟化和拉伸時災(zāi)難性失效（零延展性）的缺陷。對于塊狀金屬玻璃,應(yīng)變軟化和脆性是其作為結(jié)構(gòu)材料更廣泛應(yīng)用的主要障礙。改善機(jī)械性能的主要方法之一是通過熱機(jī)械加工實(shí)現(xiàn)再生以獲得更高能量狀態(tài)的金屬玻璃。金屬玻璃的熱機(jī)械加工可以顯著地誘導(dǎo)其結(jié)構(gòu)和性質(zhì)的變化,即使熱機(jī)械加工施加的宏觀應(yīng)變完全在彈性體系內(nèi)時依然有效。這種處理可以使得金屬玻璃達(dá)到更高能量的“回復(fù)”狀態(tài)或更低能量的“老化”狀態(tài),因?yàn)榛貜?fù)狀態(tài)能使非晶合金力學(xué)性質(zhì)得到改善,因此金屬玻璃的回復(fù)受到了廣泛的關(guān)注。研究普遍認(rèn)為,熱機(jī)械加工導(dǎo)致的結(jié)構(gòu)和性質(zhì)的變化會隨著加工程度的變化而單調(diào)變化。在本論文中,我們用超聲錘擊方法處理各種金屬玻璃,結(jié)果表明通過強(qiáng)烈的超聲彈性處理,（i）損傷和（ii）通過增加原子遷移率促進(jìn)回復(fù)之間的內(nèi)在結(jié)構(gòu)競爭可以導(dǎo)致振蕩形式的能量儲存。這一現(xiàn)象和在玻璃形成液體的粘性流動中看到的情況類似,但是在彈性狀態(tài)下處理玻璃會產(chǎn)生更高的振蕩幅度。我們在La基金屬玻璃的低溫?zé)嵫h(huán)過程中觀察到能量振蕩,這表明在高頻率彈性處理過程中能量振蕩是MG的一般特征。存儲能量的振蕩行為的發(fā)... 

【文章來源】：中國科學(xué)院大學(xué)(中國科學(xué)院物理研究所)北京市

【文章頁數(shù)】：99 頁

【學(xué)位級別】：博士

【文章目錄】：
摘要
Abstract
Chapter1 Introduction
    1.1 Metallic glasses and their unique properties
    1.2 Achilles’heel in mechanical performance of MGs
    1.3 Methods to improve room temperature plasticity in MGs
        1.3.1 Fabrication of amorphous/(nano)crystalline composites
        1.3.2 Design of BMGs with specific compositions
        1.3.3 Size reduction of MGs
        1.3.4 Thermomechanical processing of MGs
    1.4 Rejuvenation of MGs induced by TMP
    1.5 Relaxation of MGs induced by TMP
    1.6 Motivation and objectives
Chapter2 Experimental methods
    2.1 Selection of materials
    2.2 Preparation of MGs
    2.3 Treatment of MGs
        2.3.1 Ultrasonic hammering(UH)process
        2.3.2 Cryogenic thermal cycling(CTC)
    2.4 Characterization of MGs
        2.4.1 X-ray diffraction(XRD)
        2.4.2 Transmission electron microscopy(TEM)
        2.4.3 Differential scanning calorimetry(DSC)
        2.4.4 Resonant ultrasound spectroscopy(RUS)
        2.4.5 Compression tests
        2.4.6 Scanning electron microscope(SEM)
        2.4.7 Vickers microhardness
        2.4.8 Temperature measurements in UH process
        2.4.9 Dynamic mechanical analysis(DMA)
Chapter3 Deformation behavior during UH
    3.1 Elastic deformation in Zr-based MGs
    3.2 Thermoplastic deformation in Pd-based and La-based MGs
    3.3 Correlations between glass properties and deformation behavior
        3.3.1 Correlations between fragility and energy dissipation
        3.3.2 Correlations betweenβ-relaxation and the extent of flow
    3.4 Summary
Chapter4 Energy storage oscillation induced by UH
    4.1 Relaxation enthalpy variations induced by UH treatment
        4.1.1 Effect of static force
        4.1.2 Effect of hammering time
        4.1.3 Effect of thermal history of as-cast MGs
    4.2 Structure-property correlations in UH-treated MGs
    4.3 Oscillatory energy storage induced by UH treatment
    4.4 Stored energy of cold work through different processing routes
    4.5 Summary
Chapter5 Finite element simulation of UH process
    5.1 Non-linear vibration due to hammering
    5.2 Finite-element-method modelling
    5.3 FEM simulation results and discussion
        5.3.1 Horn vibrations prior to loading
        5.3.2 Disk vibrations during UH
        5.3.3 Effect of static force on disk vibration
        5.3.4 Non-linear variations of the work done
    5.4 Summary
Chapter6 Energy storage behavior during CTC
    6.1 Oscillatory energy storage induced by CTC
    6.2 Effect of thermal history on energy storage evolution
    6.3 Effect of chemical heterogeneity on cryogenic rejuvenation
        6.3.1 Lanthanum impurity contents
        6.3.2 Relaxation enthalpy variations
        6.3.3 Mechanical performance
        6.3.4 Effect of chemical heterogeneity on microstructure
        6.3.5 Effect of impurity on thermomechanical properties
    6.4 Summary
Chapter7 Summary and outlook
References
個人簡歷及發(fā)表文章目錄
Acknowledgements


【參考文獻(xiàn)】：
期刊論文
[1]Serrated magnetic properties in metallic glass by thermal cycle[J]. 李明哲,Sajad Sohrabi,丁大偉,董幫少,周少雄,汪衛(wèi)華.  Chinese Physics B. 2017(06)



本文編號：3621409