热膨胀方法研究Zr基块体非晶合金的晶化过程

Study on Crystallization Process of Zr-Based Bulk Amorphous Alloy by a Heat Expansion Method

利用电弧熔炼及铜模快速铸造法制备Zr41.2Ti13.8Cu12.5Ni10Be22.5块体非晶合金,通过热膨胀法测试晶化过程,与差示扫描量热法进行对比。通过高分辨电子显微镜观察晶化初期晶核的形成和长大规律。结果表明,热膨胀系数测试块体非晶合金的结构弛豫、玻璃转变、过冷液相区、晶化开始温度和晶化过程中不同晶化峰温度与差示扫描量热法测试结果完全吻合。在高分辨像中观察到近似球形的纳米晶粒和晶格条纹。然而,在高分辨像中很难辨认出晶化初期微小的晶化区域,只有对其进行快速傅里叶变换才能发现微小区域的晶化基本特征。

Zr(41.2)Ti(13.8)Cu(12.5)Ni(10)Be(22.5) bulk amorphous alloy (BAA) was prepared by arc melting and copper mold rapid casting. The crystallization process was tested by a heat expansion method, and the results were compared with that of the differential scanning calorimetry (DSC). The formation of the crystal nucleus and the crystal growth rule at the initial stage of crystallization was observed by high resolution transmission electron microscope (HRTEM). It is found that the relaxation process of the amorphous structure, glass transition, supercooled liquid region, starting temperature of crystallization and peak temperatures of the crystallization process which were tested by heat expansion are accordant with DSC results. The near-spherical nanocrystalline grains and crystal lattice stripes can be observed in HRTEM images. However, it is difficult to identify the tiny crystallization zone by HRTEM images at the initial stage of crystallization. The basic crystallization characters of the tiny zone can be observed expediently only by the fast Fourier transform (FFT) for the HRTEM image.