氢致块体非晶化及机制研究

For the BMG-forming alloys, in which the internal factors such as the number and the nature of the components, the alloy composition is crucial for the glass formation. Therefore, the addition method usually is employed to improve the glass-forming ability of alloys. Early research shown that gas element hydrogen can make some intermetallic compounds into amorphous structure, but its effects on the glass forming ability of bulk metallic glass are rarely reported. In our previous study, we found hydrogen can improve the glass forming ability of bulk metallic glasses after melt hydrogenation. This project is proposed to expand the hydrogen-induced amorphization to bulk metallic glasses. Firstly, the process of melt hydrogenation is studied, and the law of diffusion and dissolution of hydrogen are gained. It can provide theoretical support for precise control of hydrogen content in the process of melt hydrogenation. In addition, the hydrogen of dispersal behavior in amorphous alloy is studied using unique diffusivity of atomic hydrogen, and it can explore structure characteristics of the amorphous alloy. Then the effects of melt hydrogenation on the glass forming ability of amorphous alloy are studied. The Gibbs free difference, fragility parameter and critical cooling rate are gained. The formation mechanism of hydrogen-induced bulk amorphization will been interpreted from the thermodynamic and kinetic points of view. The results of project research are expected to be of significance on the preparation of bulk metallic glasses by melt hydrogenation.

制备块体非晶合金时，组元的数量和性质、合金成分都是影响非晶合金形成的内在因素，所以元素添加法常常被用于提高合金的玻璃形成能力。早期研究表明，气体元素氢可以促使一些金属间化合物发生非晶化，而其对块体非晶合金形成能力的影响却鲜有报道。申请人前期研究发现，对非晶合金进行液态置氢后可以提高其玻璃形成能力。本项目拟将氢致非晶化技术拓展到块体非晶合金中，首先研究非晶合金的液态置氢过程，获得液态置氢条件下氢的扩散与溶解规律，为精确控制液态置氢过程中的置氢量提供理论支持。此外，利用氢原子独特的扩散性，研究其在非晶合金中的扩散行为，探索非晶合金的结构特征。之后，研究液态置氢对非晶合金玻璃形成能力的影响，获得置氢后非晶合金吉布斯自由能差、脆性参数、临界冷却速度的变化规律，从非晶合金的形成热力学、动力学角度揭示氢致块体非晶化形成机制。项目成果有望对利用液态置氢技术制备块体非晶合金发挥重要作用。

液态置氢法可以有效提高Zr64Cu24Al12与Zr66Cu22Al12合金的玻璃形成能力，当氢含量达到201 wppm和198 wppm时，两种合金的玻璃形成能力达到最大，临界尺寸为4.5 mm和3.5 mm。研究发现，置氢后的非晶合金，随着升温速率的提高，两个放热峰均向高温方向移动，表现出很强的动力学特征。而相同升温速率下，置氢后非晶合金的过冷液相区宽度、约化玻璃转变温度和晶化激活能增大，脆性参数降低，在10%H2时最低，从热力学与动力学角度揭示了氢致非晶合金提高的原因。研究发现，金属元素内壳层电子约束能随着氢含量的增加总的趋势是先减小到最小值然后又增大，在氢含量为10%时，结合能达到最小值，原子之间的电荷随着原子间距减小造成的外壳层电子的交叠，电荷对原子核所产生的屏蔽作用增加，使约束能向低能量方向移动，形成更加密实的密堆结构；充氢量为10%时合金具有最多数目的化学键，增大原子长程扩散以及合金晶化相析出的难度，极大地提高了锆基块体非晶合金的玻璃形成能力。项目中的液态置氢法对提高体系的玻璃形成能力方面显示了较大的优势，为提高非晶合金玻璃形成能力提供了一条新的途径。