金属间化合物强动力学效应对非晶转变的作用机制研究

The alloys which can form glass phase or experience glass phase transition usually contain intermetallic compound, indicating that the intermetallic compound has its specific effect. Comapred with solid solution, the intermetallic compound grows in a manner of two-demension nucleation or screw dislocation. In this case, a high kinetic undercooling can be obtained, thus the total undercooling increases drastically. This maybe the reason why amorphourization occurs easily. The previous investigations on this aspect mainly focused on the effect of the complex liquid structure of the intermetallic compound melt on the glass formation and glass phase transition. However, few works consider the contribution of the kinetic undercooling. This project will investigate the intrinsic mechanisms of the effect of the intermetallic compound from the point of view of the kinetic effect...For this purpose, Ni-Nb and Pd-Cu-Si systems will be selected as the research objects. The former alloy, both of the two eutetic phases are intermetallic compounds, has been reported to form glass phase during solidification. While the later alloy, which also contain the intermetallic compound phases, can experience a "eutectic-glass" direct transition at a velocity in the order of magnitue of mm/s. By using these two alloys, eutectic to other crystalline structure transition or eutectic to glass phase transition will be realized. The amellar spacing and grwoth velocity when the transiton takes place will be measured for the Ni-Nb alloys. For the Pd-Cu-Si alloy, the total undercooling will be determined. The kinetic undercooling is then examined. On the basis of the measurement, the effect of the kientic effect of the intermetallic compound on the decrease of the diffusion coefficient will be studied. Because the sluggish diffusivity is a key factor for the glass phase transition, the function of the intermetallic compound on the drastic decrease of the diffuisive ability and their interactive effect on the glass phase formation will be checked and elucidated quantitatively. The results of this project will provide an in-depth insight into the glass formation mechanism and be helpful for searching new glasses.

含有金属间化合物相的合金易发生非晶转变，说明金属间化合物对非晶转变有其内在的作用机理。同固溶体相比，金属间化合物生长以二维形核或螺旋位错方式进行，动力学过冷度相对较大，所以含金属间化合物的共晶组织易获得深过冷，有可能导致非晶形成，但相关作用机制并不清楚。已有研究主要集中在金属间化合物熔体结构等对非晶转变的影响方面，而鲜有从动力学效应入手，因此无法揭示其对非晶转变的内在机理，亟待深入研究。本项目选用共晶相均为金属间化合物的Ni-Nb共晶合金和在毫米/秒速度条件下就发生"共晶-非晶"直接转变的Pd-Cu-Si合金，实现共晶到其它晶体形貌或非晶的转变，对于前者测量共晶转变的层片间距及生长速度，对于后者直接测量总过冷度，由此确定动力学过冷度，阐明其对扩散系数的影响规律，结合非晶合金体系扩散系数随过冷度增大显著减小的脆性特点，揭示强动力学效应对非晶相形成的作用机理，为设计新型的非晶合金提供理论依据。

本项目在含有金属间化合物相的共晶合金系易发生非晶转变、但其作用机制还不清楚的前提下，基于金属间化合物生长以二维形核或螺旋位错方式进行、动力学过冷度相对较大的特点，开展了此类合金系生长控制过程中的“共晶-非晶”转变定量研究。主要完成的内容有：（1）Ni-Nb合金系的非晶转变机理：得用激光熔凝技术，完成了其外延生长，获得了其“共晶-非晶”转变界面处的生长速度和层片间距，阐明了其转变规律；2）在定向凝固条件和激光熔凝条件下研究了Pd77Cu6Si17合金的凝固行为，获得了“共晶-非晶”转变时的定量参数，揭示了其转变机理；3）利用高分子材料的搭台生长与金属间化合物二维形核方式相似的特点，定量研究了高分子共聚体系的生长，阐明了其强动力学效应；4）非fragile型合金中的金属间化合物由于扩散系数较大，很难获得非晶相。.以上研究阐明了金属间化合物在非晶转变过程的作用规律，揭示了扩散系数和动力学效应相互作用对获得非晶相的作用机制，为设计新型的非晶合金提供了理论依据。以此为基础，在国内外学术期刊上发表学术论文14篇，被SCI收录13篇次；获陕西省科学技术三等奖1项，培养硕士生3人，博士生2人。