目的 通过超声滚压提高Ti-6Al-4V的屈服强度。方法 将超声振幅作为唯一变量，设置0、5、7、10 μm 4组试验，分析Ti-6Al-4V被加工表面及表面以下30~50 μm处的应力应变行为。通过X射线衍射仪(XRD)测试不同超声振幅下Ti-6Al-4V的两相分布。采用扫描电子显微镜(SEM)，分析不同超声振幅下Ti-6Al-4V表面层塑性变形程度。使用能谱仪(EDS)观察不同超声振幅下Ti-6Al-4V表面层元素组成分布。通过万能试验机获得不同超声振幅下Ti-6Al-4V的应力应变曲线。结果 Ti-6Al-4V表面层塑性变形程度随着超声振幅的增大而增大。Ti-6Al-4V被加工表面的β相体积分数随着超声振幅的增大呈先减小后增大的趋势。当超声振幅为7 μm时，Ti-6Al-4V被加工表面β相的体积分数最大(19.70%)。超声滚压Ti-6Al-4V表面层中β相的体积分数沿深度递减。Ti-6Al-4V表面层α相稳定元素Al和β相稳定元素V未出现明显与两相体积分数相同的变化趋势。Ti-6Al-4V材料的屈服强度随着超声振幅的增大呈先减小后增大的趋势。当超声振幅从5 μm增至10 μm时，Ti-6Al-4V的屈服强度依次为1.06、1.03、1.16 GPa，相较于在无超声加工下的Ti-6Al-4V屈服强度(0.91 GPa)分别提高了约16.48%、13.19%和27.47%。结论 超声振幅的增大，可以增大滚压过程中Ti-Al-4V的塑性变形程度。合适的超声振幅，可以改变Ti-6Al-4V表面层两相分布。经超声滚压后，Ti-6Al-4V的屈服强度受到材料塑性变形和两相分布的共同影响，且Ti-6Al-4V的塑性变形程度对屈服强度的影响更大。

To improve the yield strength of titanium alloy Ti-6Al-4V material by ultrasonic burnishing, ultrasonic amplitude was used as the unique variable in this work. Four groups of experiments were set to analyze the stress-strain behavior of titanium alloy Ti-6Al-4V material on the machined surface and 30-50 μm below the surface. Ultrasonic amplitude in four groups was set as 0, 5, 7 and 10 μm, respectively. The burnishing of Ti-6Al-4V material without ultrasonic vibration was adopted as the control group. Two-phase distributions of titanium alloy Ti-6Al-4V material on the machined surface and 30-50 μm below the surface were measured by X-ray diffractometer (XRD). Scanning Electron Microscope (SEM) was used to analyze the plastic deformation degree of titanium alloy Ti-6Al-4V grains in the machined surface layer at different ultrasonic amplitudes. Energy Dispersive Spectrometer (EDS) was applied to observe the composition element distribution of the burnished titanium alloy Ti-6Al-4V surface layer under different ultrasonic amplitudes. Universal testing machine was used to obtain the various stress-strain curves of the burnished titanium alloy Ti-6Al-4V samples at different ultrasonic amplitudes. Lastly, the change rules of stress-strain behavior, plastic deformation and two-phase distribution for the burnished titanium alloy Ti-6Al-4V under different ultrasonic amplitudes were comparatively analyzed. The effect of microstructure on the stress-strain behavior for the ultrasonic burnished titanium alloy Ti-6Al-4V was clarified. Results indicated that the plastic deformation degree of titanium alloy Ti-6Al-4V grain increased with ultrasonic amplitude. The volume fraction of β phase for the ultrasonic burnished titanium alloy Ti-6Al-4V decreased firstly and then increased with the increase of ultrasonic amplitude. When ultrasonic amplitude was 7 μm, the volume fraction of β phase on the burnished titanium alloy Ti-6Al-4V surface reached the maximum value 19.70%. The volume fraction of β phase in the titanium alloy Ti-6Al-4V surface layer decreased along the depth during ultrasonic burnishing. However, stable element Al for α phase and stable element V for β phase did not show the obvious trend of the same rules with the increase of ultrasonic amplitude. After ultrasonic burnishing, the yield strength of titanium alloy Ti-6Al-4V showed a trend of decrease firstly and then increased with the increase of ultrasonic amplitude. When ultrasonic amplitude increased from 5 μm to 10 μm, the yield strength value of the ultrasonic burnished Ti-6Al-4V material was 1.06 GPa, 1.03 GPa and 1.16 GPa, respectively. Compared to the yield strength value 0.91 GPa of titanium alloy Ti-6Al-4V burnished without ultrasound, the yield strength of the ultrasonic burnished Ti-6Al-4V increased by 16.48%、13.19% and 27.47%, respectively. When ultrasonic amplitude was 10 μm, the yield strength of titanium alloy Ti-6Al-4V material reached the maximum. The increase of ultrasonic amplitude can increase the plastic deformation degree of the burnished titanium alloy Ti-6Al-4V material. Appropriate ultrasonic amplitude can change the two-phase distribution of the ultrasonic burnished titanium alloy Ti-6Al-4V. The yield strength of titanium alloy Ti-6Al-4V is commonly affected by the plastic deformation and two-phase distribution of material after ultrasonic burnishing. The plastic deformation degree of titanium alloy Ti-6Al-4V material has a greater impact on the yield strength.