Influence of Grain Refiners on the Wettability of Al2O3 Substrate by Aluminum Melt

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2021-02, Vol.52 (1), p.382-392
• Main Authors: Yang, Jiawei, Bao, Sarina, Akhtar, Shahid, Shen, Ping, Li, Yanjun
• Format: Article
• Language: English
• Subjects: Adhesive strength; Aluminum oxide; Characterization and Evaluation of Materials; Chemistry and Materials Science; Contact angle; Droplets; Grain refinement; Master alloys; Materials Science; Melts; Metallic Materials; Nanotechnology; Sedimentation; Sedimentation & deposition; Solidification; Structural Materials; Substrates; Surface layers; Surfaces and Interfaces; Thin Films; Wettability; Wetting
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-020-01989-4

It is well known that grain refiner additions in aluminum melts significantly reduce the filtration efficiency of ceramic foam filters (CFF). However, the mechanism remains unclear. In this work, the influence of grain refiners on the wettability of alumina substrate by aluminum melt was studied by both conventional sessile drop and improved sessile drop methods at different temperatures and vacuums. Commercial purity aluminum (CP-Al) and grain refiner master alloys Al-3Ti-1B, Al-5Ti-1B, Al-3Ti-0.15C were used. It is found that master alloy melts wet alumina substrate better than CP-Al. Generally, a lower temperature or lower vacuum results in a higher contact angle. The roles of grain refiner particles in improving the wettability were studied by analyzing the solidification structure of post wetting-test droplets using SEM. Strong sedimentation of grain refiner particles at the metal-substrate interface was observed, which is attributed to the higher density of grain refiner particles compared to the Al melt. Meanwhile, a large fraction of grain refiner particles agglomerates at the oxide skin of the aluminum droplets, showing a strong adhesion between the particles and oxide skin. Such adhering of grain refiner particles is proposed to enhance the rupture of the original oxide skin of the droplets and slow down the reoxidation process at the surface layer. Both adherence of grain refiner particles to surface oxide skin and sedimentation of particles at the metal-substrate interface are responsible for the wetting improvement.