Fragmentation-driven grain refinement in directional solidification of AlCu10wt-% alloy at low pulling speeds. (March 2017)

• Record Type: Journal Article
• Authors: Zimmermann, G.; Pickmann, C.; Hamacher, M.; Schaberger-Zimmermann, E.; Neumann-Heyme, H.; Eckert, K.; Eckert, S.
• Is Part Of: Acta materialia. Volume 126(2017)
• Page Start: 236
• Page End: 250
• Publication Date: 2017-03
• Subjects: Aluminum alloy -- Solidification -- In-situ X-ray diagnostic -- Fragmentation -- Grain structure; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2016.12.063
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The formation of the grain structure in Al-10 wt%Cu alloy during directional solidification was investigated experimentally. The alloy composition was chosen because of its special feature that both the initial melt composition and the solidifying primary Al dendrites have almost identical densities. Therefore, gravity-related effects such as buoyancy or sedimentation acting on nucleated or fragmented solid particles in the melt are expected to be minor. In 3D bulk samples at low solidification velocities, unexpected equiaxed grain growth was found instead of columnar growth. This behavior was investigated in accompanying solidification experiments with thin samples using in-situ X-ray diagnostics. It is demonstrated that fragments detach from the dendrite tip region and move slightly ahead of the solid-liquid interface as they grow. As a result, a dendritic microstructure consisting of elongated equiaxed grains is developed. Accordingly, fragmentation was identified as responsible for grain refinement in the given parameter range. Graphical abstract: Image 1