非晶合金晶化峰位置与晶化工艺参数间关系的研究

Understanding the crystallization kinetics of amorphous alloys is vital for their proper applications and exploiting the promising potential. Recently, it was found that the interval between crystallization peaks in some special amorphous alloys possesses a completely different changing trend with decreasing heat rate from most of amorphous alloys. Up to now, systematically theoretical exploration of this question remains unreported. Hence, in this project, some typical amorphous alloys will be employed for isochronal crystallization experiments in a wide range of heating rates and isothermal crystallization experiments within a large temperature range, respectively, to investigate the change of the crystallization peak positions with crystallization process parameters such as the heating rate and isothermal temperature. By characterizing the microstructure and the 3D element distribution in the samples crystallized up to different stages, and analyzing the crystallization kinetics for each crystallization reaction, the dominant factor underlying the movement of crystallization peaks with crystallization process parameter will be determined, and the mechanism for the movement will be clarified. Moreover, isochronal crystallization of the amorphous/amorphous composites will also be carried out to investigate the crystallization sequence between the two amorphous phases under different heating rates, and to put forward the principle for designing amorphous/amorphous composites whose primary crystallization phase is capable of replacing. The investigation is an important complement to crystallization kinetics theory, and will also greatly enrich the designing theory of amorphous matrix composites.

认识非晶合金的晶化动力学行为是正确使用该类材料、挖掘其性能潜力的重要前提。近期在个别非晶合金连续加热晶化的实验中发现：降低加热速率，晶化峰间距离的变化方向与大多数非晶合金相反，对之目前尚未有系统的理论阐述。为此，本项目拟筛选具有代表性的非晶合金，进行宽加热速率范围内的连续加热晶化实验和宽温度范围内的等温晶化实验，考察热分析曲线上晶化峰位置随晶化工艺参数（连续加热速率、等温晶化温度）的变化情况，分析晶化不同阶段的组织及三维空间中的成分分布，对各晶化反应进行动力学分析，探讨晶化峰相对位置随加热法工艺参数变化的控制性因素及其内在机制。此外还将开展非晶/非晶复合材料的连续加热晶化实验，考察两非晶相的晶化顺序与加热速率的关系，提出晶化对象可调整的非晶/非晶复合材料的设计准则。相关工作将是对相变动力学理论的重要补充和完善，同时也将极大丰富非晶基复合材料的设计理论。

非晶合金晶化行为是当今非晶领域热点研究内容之一，通过合理调控非晶合金晶化工艺获得部分晶化的非晶基复合材料有望实现性能的进一步改善。根据热分析动力学，晶化激活能相差较大的晶化事件随加热速率变化而导致的晶化温度变化并不相同，这意味着在宽加热速率条件下相邻晶化事件的顺序可能发生转变，对此目前尚未有系统的理论阐述，更缺乏利用这一晶化特点的材料设计。为此，本项目通过对Al基、Zr基、Cu基非晶合金晶化峰位置、晶化顺序与晶化工艺参数关系的研究，分析了影响非晶合金晶化峰位置和晶化顺序随晶化工艺参数变化的因素，提出了晶化对象可调节的非晶-非晶复合材料的设计原则。结果表明：Al-Ni-La-Si单相非晶合金20 K/min加热速率时的第二、第三晶化顺序在宽加热速率下不会发生逆转，与热分析动力学计算相悖，这说明非晶合金晶化峰位置随晶化工艺的变化不单是一个热分析动力学问题，元素再分配也决定了晶化事件之间的顺序。借助于Si、Ti元素添加对Zr基非晶合金晶化激活能影响的研究，发现元素添加对不同晶化相析出的晶化激活能会产生不同影响，进而改变晶化工艺参数对各晶化峰位置的影响。上述研究结果结合热分析动力学方程，提出设计可调节的非晶-非晶复合材料应满足各组成非晶合金晶化峰晶化激活能相差较大、各晶化过程独立且晶化产物易于区分等条件。目前项目已发表论文13篇，预计培养硕士研究生6名。