Experimental Study on Ultrasonic Testing of TC4 Titanium Alloy by Additive Manufacturing

Research about ultrasonic testing was carried out for different processing states (hot isostatic and heat treated) of the additive manufacturing TC4 titanium alloy (Ti-6A1-4V) by electron beam rapid manufacturing technique. Firstly, the longitudinal wave velocity and attenuation coefficient of the parts in these two processing states were measured by the contact longitudinal wave reflection method. Then, the signal-to-noise ratio of the phi 0.8mm flat bottom hole defect buried depth 20-50mm was studied by using the water immersion ultrasonic method, the ultrasonic testing parameters and detection methods for different processes were analyzed. The results show that for the same processing state, the longitudinal wave velocity parallel to the deposition direction is significantly higher than that perpendicular to the deposition direction, and the attenuation coefficient is smaller than that perpendicular to the deposition direction; For the situation of different processing states, compared with the hot isostatic state, the longitudinal wave velocity of the material in heat treatment state is obviously reduced, and the attenuation coefficient is relatively close. For defects with buried depth of not more than 40 mm, it's more effective to detect the defects in the direction perpendicular to the deposition direction, within the heat treatment state, the signal-to-noise ratio is relatively high; When the buried depth is greater than 40mm, the signal-to-noise ratio is significantly reduced, and the detection result can he optimized by setting correct DAC curve.