快速凝固AlNiCuNd纳米/非晶复合材料的制备及显微组织研究

Preparation of Rapidly Solidified Al-Ni-Cu-Nd Aluminium Based Amorphous Composites with Nanocrystal Phase and Its Microstructural Characteristics

采用熔体单辊旋淬法制备了快凝Al87Ni7Cu3Nd3合金条带,利用差热扫描热力学(DSC)分析、X射线衍射(XRD)分析等手段对比研究了快凝合金条带及其不同退火态材料的晶化行为。选择合适工艺条件,对快凝合金条带进行等温加热退火,采用高分辨透射电镜(HRTEM)观察分析了等温退火态材料显微组织特征。结果表明,快凝Al87Ni7Cu3Nd3合金薄带呈现出完全均匀的非晶态结构。随加热温度升高,非晶态薄带的晶化过程包括两个主要的相转变:α—Al晶体从非晶基体中析出的初始晶化以及有Al3Ni,Al11Nd3和Al8Cu3Nd形成的第二次晶化过程。在低于310℃下加热,快速凝固Al87Ni7Cu3Nd3金属玻璃中发生的主要相转变是富Al非晶的初始晶化。110℃等温退火态薄带主要是由α-Al加残余非晶相的两相组成,α—Al晶体纳米颗粒均匀弥散分布在残余非晶基体上。而在310℃热暴露后的退火试样中,在除α-Al晶体外的残留非晶相中开始出现极少量的Al3Ni金属间化合物。

Rapidly solidified Al87 Ni7Cu3Nd3 metallic glass ribbons were prepared by using melt spinning, and were treated under both continuous heating and isothermal heating regime. The amorphous ribbons and the annealed samples were closely examined by means of differential scanning calorimetric, conventional X-ray diffraction, and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in primary crystallization into α-Al nanocrystalline particles, in order to understand structural characteristics of the aluminium-based amorphous composites with nanocrystal particles. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale. With heating temperature inproving, the amorphous ribbons devitrify via two main stages: primary crystallization, resulting in a-Al crystal particles precipitation from the amorphous matrix, and secondary crystallization, corresponding to some inter-metallic phases appearing, including Al3Ni, Al11Nd3, and Al8Cu2Nd. The main phase transformation in the amorphous ribbons is primary crystallization when heating below 310 ℃ . The ribbons annealed isothermally at 110 ℃ consist of two-phase mixture of the α-Al crystal phase and the residual amorphous phase, the α-Al crystal nanometer particles dispersing uniformly in an amorphous matrix, while a very small amount of Al3Ni intermetallic compound begin appearing, besides the α-Al crystal, in the residual amorphous phase of the ribbons heated up to 310 ℃.