*3.1. E*ff*ect of the Ultrasonic Bending Vibration on the Grain Microstructure of the 1060 Aluminum Alloy Cast Rolling Strip and Subsequent Cold Rolling Strip*

The microstructure of the 1060 aluminum alloy after continuous casting and rolling is shown in Figure 3. It can be seen from the figure that the grains on the upper surface of the cast rolling strips are obviously elongated and have become fibrous; on the longitudinal section of the cast rolling strips, the grains are also fibrous. In comparison, it was found that the fibrous grains of the ultrasonic cast rolling strip tested with the 0.18 wt% Al-Ti-B refiner and the ultrasonic cast rolling strip tested with the 0.12 wt% Al-Ti-B refiner were finer, with average grain sizes of approximately 39.6 µm and 34.5 µm, respectively. The average grain size of the conventional cast rolling strip tested with the 0.18 wt% Al-Ti-B refiner was about 50.2 µm, and the grain size of the ultrasonic cast rolling strip tested with the

0.09 wt% Al-Ti-B was somewhat coarse and unevenly distributed, and the average grain size was about 54.0 µm. On the cross section of the cast rolling strips, the grain size of the ultrasonic cast rolling strip tested with the 0.18 wt% Al-Ti-B refiner and the ultrasonic cast rolling strip tested with the 0.12 wt% Al-Ti-B refiner were fine and uniform, and the average grain size was about 29.5 µm and 28.6 µm, respectively. Meanwhile, the average grain size of the conventional cast rolling strip with the 0.18 wt% Al-Ti-B refiner was about 33.4 µm, and that of the ultrasonic cast rolling strip with the 0.09 wt% Al-Ti-B refiner was coarser and unevenly distributed, with an average grain size of about 35.1 µm. μ μ μ μ

**Figure 3.** Grain microstructure of the 1060 aluminum alloy cast rolling strips: (**a**–**c**) the top surface, longitudinal section, cross section of the strip with added 0.18 wt% Al-Ti-B refiner and applied conventional treatment; (**d**–**f**) the top surface, longitudinal section, cross section of the strip with added 0.18 wt% Al-Ti-B refiner and applied ultrasonic treatment; (**g**–**i**) the top surface, longitudinal section, cross section of the strip with added 0.12 wt% Al-Ti-B refiner and applied ultrasonic treatment; (**j**–**l**) the top surface, longitudinal section, cross section of the strip with added 0.09 wt% Al-Ti-B refiner and applied ultrasonic treatment.

It can be seen from the above comparison that under the same 0.18 wt% Al-Ti-B refiner addition, the average grain size of the ultrasonic cast rolling strip was significantly smaller than that of the conventional cast rolling strip, indicating that the ultrasonic bending vibration could effectively refine the grain microstructure of the cast rolling strips. When the Al-Ti-B refiner addition was reduced to 0.12 wt%, the average grain size of the ultrasonic cast rolling strip was still smaller than that of the conventional cast rolling strip, but when the Al-Ti-B refiner addition was reduced to 0.09 wt%, the grain sizes of the ultrasonic cast rolling strip also became coarse and uneven, and the average grain size exceeded that of the conventional cast rolling strip with 0.18 wt% Al-Ti-B refiner.

The microstructure of the 1060 aluminum alloy cast rolling strip after the subsequent cold rolling is shown in Figure 4. Compared with the conventional cold rolling strip, the ultrasonic cast rolling strip with 0.18 wt% Al-Ti-B refiner or 0.12 wt% Al-Ti-B refiner had an obvious fiber structure that was finer and more uniform, without obvious blocks; the 0.18 wt% Al-Ti-B refiner-added ultrasonic cast rolling strip had the finest fiber structure after cold rolling. However, the 0.09 wt% Al-Ti-B refiner-added ultrasonic cast rolling strip had the tendency to coarsen the fiber grains after cold rolling.

**Figure 4.** Grain structure after the subsequent cold rolling of the 1060 aluminum alloy cast rolling strip: (**a**) the top surface of the strip with added 0.18 wt% Al-Ti-B refiner and applied conventional treatment; (**b**) the top surface of the strip with added 0.18 wt% Al-Ti-B refiner and applied ultrasonic treatment; (**c**) the top surface of the strip with added 0.12 wt% Al-Ti-B refiner and applied ultrasonic treatment; (**d**) the top surface of the strip with added 0.09 wt% Al-Ti-B refiner and applied ultrasonic treatment.
