搅拌摩擦焊(Friction stir welding, FSW)薄板检测历来是一个难点，现在应用于薄板焊缝检测的方法多采用横波入射法及超声相控阵扇形扫查等，但这些方法都难以实现长直焊缝的快速检测与缺陷成像。采用超声相控阵C扫描直接从焊缝表面对焊缝内部缺陷进行C扫描，研究该技术对不同厚度薄板隧道型及未熔合缺陷的探测能力，开发一套用于快速相控阵检测的机械装置，并分析FSW焊缝表面对C扫描成像的影响。试验结果证明，采用超声相控阵技术对5 mm以上厚度板中0.3 mm以上的侧孔及0.5 mm的平底孔具有良好的检测效果。

It has been a difficult problem to detect the defects in aluminum alloy friction stir welding(FSW) joints, especially those in thin plates. Recently most of the methods adopt the transverse wave or the ultrasonic phased array S-scan. However, these means cannot present all of the defects in a single picture effectively and efficiently. Ultrasonic phased array technology is used to detect the inner defects just above the upper surface of the weld by C-Scan on different sorts of defects in plates with various thickness. A mechanical device is developed to accelerate the procedure of detection. What’s more, the influence of the roughness of the FSW surface on its detectability is analyzed. The results of the experiments show that 0.3 mm-diameter side hole and 0.5 mm-diameter flat bottom holes in a 5 mm-thick flat plate can be detected effectively with the help of ultrasonic phased array.