Fig. 3: Effect of ultrasound on grain structure of Inconel 718 single tracks.

a–f Cross-section inverse pole figure (IPF) plots of single tracks without ultrasound (a), with low-intensity ultrasound of 10.5 W·cm⁻² (b), 14 W·cm⁻² (c) and 17.5 W·cm⁻² (d), and with high-intensity ultrasound of 212.4 W·cm⁻² (e) and 849.6 W·cm⁻² (f). g–i Lateral IPF plots of single tracks (profile along scanning direction of the single fusion track) with the ultrasonic intensity of 0 W·cm⁻² (g), 17.5 W·cm⁻² (h) and 849.6 W·cm⁻² (i). j Variations of grain size and aspect ratio (the ratio of grain length to width) of the single tracks with the ultrasonic intensity from 0 to 849.6 W·cm⁻². To avoid the influence of the unique thermal environment on the top of the fused track and substrate on grain growth, the analysis of the grain size and aspect ratio is limited in the central region of the sample (the region selected by the white box in Fig. 3a–f). Details of the grain size distribution of Inconel 718 single tracks can be found in Supplementary Fig. 6. The length of error bars in Fig. 3j indicates the dispersion of data in three tests.