Anisotropic acoustic properties of directionally solidified nickel-based superalloy DZ444

Abstract

Directionally solidified nickel-based superalloy DZ444 specimens with different directions were selected. The crystal orientation and microstructure were characterized by electron back-scattered diffraction technique and so on. The longitudinal wave velocity and attenuation coefficient were analyzed by ultrasonic pulse-echo technique. Results show that the above two acoustic properties are anisotropic. With the included angle φ between the normal direction of the sheet plane and the solidified direction increases from 0° to 45° to 90°, the longitudinal wave velocity increases from 5533m/s to 6595m/s and then decreases to 5634m/s, while the attenuation coefficient shows a monotonic increment of 0.19dB/mm. Further spectrum analysis shows that the main frequency shift, amplitude shift and apparent integral reflection coefficient of the surface echo and the bottom echo present a similar trend with the attenuation coefficient. This is mainly resulted by the difference of microstructure and crystal orientation.

Keywords

• directional solidification
• nickel-based superalloy
• acoustic property
• anisotropy
• spectrum analysis