单晶等材料的性能表征因其各向异性存在许多技术方法局限性。超声是一种成熟且经济实用的技术，超声信号蕴含着丰富的材料宏观和微观结构等信息。为利用超声技术优势表征单晶高温合金的各向异性，本工作提出了一种能获得超声各向异性传播声场可视化表示的表面纵波全方向扫查(SLW-ODS)测试方法。首先通过理论分析和仿真明晰了单晶材料中表面纵波的激励接收技术条件，然后搭建了水浸超声环形扫描检测试验平台，对晶体生长取向为<001>和<011>的镍基单晶高温合金试样以及各向同性的不锈钢板和电解镍板进行了测试，通过检测表面纵波在传播过程中泄漏到水中的波，获得了四种试样的表面纵波传播声场。再通过提取环形声场信号构建极坐标下的全向声时幅度分布的图像(OATM)，并采用图像处理技术获得了各方向准确的相对声速，与基于Christoffel方程的理论速度曲线高度一致。结果表明，基于SLW-ODS方法获得的不同形态花纹图案的OATM可方便地表征单晶高温合金的各向异性。

The performance characterization of single-crystal materials faces numerous technical limitations owing to their intrinsic anisotropy. Ultrasonic testing, a mature and cost-effective technique, provides rich information about both macroscopic and microscopic structural properties of materials. While it has been widely used to characterize the microstructures and mechanical properties of isotropic materials, its applications to anisotropic materials remain limited owing to the complexity of their acoustic behavior. Recent advancements driven by the competitive demands of the aerospace industry have made this field a research hotspot. To leverage ultrasonic technology for characterizing anisotropy in single-crystal superalloys, this study proposes a surface longitudinal wave omnidirectional scanning (SLW-ODS) method that enables the visual representation of ultrasonic wave propagation fields in anisotropic media. The core approach involves exciting SLWs in the workpiece, combined with surface acoustic field imaging and morphological image processing techniques, to map and analyze the macro- and micro-structural and mechanical anisotropy of single-crystal superalloys. First, the technical conditions for SLW excitation and reception in single crystal materials were clarified through theoretical analysis and simulation. Then, a water-immersion ultrasonic ring-scanning test platform was developed to examine nickel-based single crystal superalloy plates with <001> and <011> crystal growth orientations as well as isotropic stainless steel and electrolytic nickel plates. The SLW propagation sound fields in the four specimens were obtained by detecting waves leaking into water during propagation. By extracting annular sound field signals in polar coordinates, an omnidirectional amplitude of flight-time distribution map (OATM) was constructed. Image processing techniques were then employed to obtain accurate relative velocities in all directions, which closely matched theoretical velocity curves derived from the Christoffel equation. The results demonstrate that OATM, with distinct morphological patterns obtained via the SLW-ODS method, effectively reflects the anisotropic acoustic characteristics of bulk waves and multimode ultrasonic waves in single crystal superalloys. These acoustic features can be further utilized to characterize anisotropy in the macro- and micro-structures and mechanical properties of single crystal superalloys.