为改善TC4钛合金激光焊接质量，引进超声振动场辅助激光焊接工艺，即超声跨态处理(UPPLW)，通过改变超声场强度，采用三圆截点法研究超声功率对激光焊接接头微观组织的影响，利用可靠性理论对数据进行分析。结果表明，在外加辅助超声场作用下，随着超声功率的增加，焊缝组织晶粒有逐渐细化的趋势，当超声功率为1600 W时，试样焊缝组织的晶粒度较常规方法获得的细化了15.8%。最后分析了超声跨态处理工艺细化组织晶粒的机理。

In order to improve the laser welding quality of TC4 titanium alloy, a technology named ultrasonic processing across different phases based on laser welding (UPPLW) is introduced. With the three-circle-cutoff-point method, the effect of ultrasonic vibration field power on the microstructures of laser welding joints is studied by changing the intensity of ultrasonic vibration field, and the measured data are analyzed based on the reliability theory. The results show that, under the influence of the ultrasonic vibration field, with the increase of ultrasonic vibration power, the microstructure grain of the welding joints has a tendency to be progressively refined. When the power is 1600 W, the grain is refined by about 15.8% compared with that obtained with conventional methods. The mechanism for UPPLW to refine grain is finally analyzed.