Effect of Forming Method and Direction on Microstructure and Ultrasonic Parameters of TA15 Titanium Alloy

Abstract:

In order to investigate the influence of the forming method and forming direction of TA15 titanium alloy on the microstructure and ultrasonic parameters,so as to clarify the acoustic properties of the material,the TA15 titanium alloy is manufactured by forging and laser deposition.The test specimens with the same cross hole defect and same standard size are manufactured.Ultrasonic non-destructive testing equipment is used to inspect the sample to obtain the defect amplitude,longitudinal wave sound velocity,and ultrasonic attenuation coefficient of the sample, and the optical microscope(OM)is used for the observation of the microstructure.The results indicate that the forming method affect the tissue characteristics, and then affect the ultrasonic parameters.The laser deposition manufacturing sample has obvious tissue anisotropy,which results in a large difference in ultrasonic parameters in different forming directions.Compared with laser-deposited sample,the length-width ratio of lath shape ɑ phase in the microstructure of the double-annealing sample have a decrease,resulting in an average reduction of the longitudinal sound velocity in all directions by 167 m/s and an increase by 13%~20% in attenuation coefficient.And compared with the forged sample,under the joint action of the difference between macro organization and micro organization, the X-direction and Z-direction longitudinal wave sound velocity decreases by 392 m/s and 466 m/s respectively, and the attenuation coefficient increases by 39% and 55% respectively.The research results have certain reference value for the ultrasonic non-destructive testing of laser additive parts and the non-destructive evaluation of internal defects of TA15 titanium alloy materials.

Key words:laser deposition manufacturing ; ultrasonic parameters; ultrasonic testing; TA15 titanium alloy; microstructure