Mechanism of ultrasound-induced microstructure modification in Al–Zr alloys

Free surface entrainment of oxide particles and their role in ultrasonic treatment performance of aluminum alloys

“…It clearly seen that, despite the quite different crystal structure, Al 3 Zr is tightly bound to the surface of Al 2 O 3 inclusion suggesting that such inclusions can serve as nucleation sites for the primary Al 3 Zr compounds. Similar results also have been reported by Wang et al [36] and Jung et al [37] The authors of the latter study obtained high-quality HR-TEM images revealing formation of a thin layer of γ-Al 2 O 3 phase on the surface of alumina particles. This phase was shown to have a small (111) planar mismatch with (114) plane of Al 3 (Zr,Ti) used in their experiments.…”

In-situ observations and acoustic measurements upon fragmentation of free-floating intermetallics under ultrasonic cavitation in water

“…Another important characteristic of UST-induced grain refinement is that the fragmented dendritic crystals can also significantly improve the microstructure, homogeneity, and quality of the casting, without the need of substantial amount of grain refining particles or addition of AlTiB master alloys [42] . Jung et al [43] reported that primary phase particles of the order of 10 μm or less was sufficient for α-Al nucleation. The final microstructure observed after solidification of treated melts is therefore systematically connected with the refinement capability of the formed primary phases.…”

Report on use of Inoculants in Missile Application Alloys

“…Because the processing conditions and size of the inoculant particles play a key role in refining the grain size and influencing microstructure morphology researchers have employed ultrasonic melt treatments (UST) to influence phase formation [26]. In the case of primary intermetallic particles and alpha-Al using pure Al and Al-Zr alloys (Al-0.3Zr-0.1Ti, Al-0.5Zr, Al-0.5Zr-0.5Mg-0.9Si) solidified at various cooling rates of 0.2-70 K s (-1), UST decreased the size and increased both the number density and volume fraction Al3Zr and Al-3(Zr,Ti) particles.…”