Microstructural coarsening of semi-solid aluminium alloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 496; no. 1; pp. 439 - 446
• Main Authors: Atkinson, H.V., Liu, D.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.11.2008; Elsevier
• Subjects: Alloys 2014 and 201; Coarsening; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Physics; Semi-solid; Spheroidal microstructure; Treatment of materials and its effects on microstructure and properties; Spheroidal microstructure; Semi-solid; Alloys 2014 and 201; Coarsening; Grain boundaries; Partial melting; Cooling; Aluminium alloys; Transition elements; Recrystallization; Semi solid state; Microstructure
• DOI: 10.1016/j.msea.2008.06.013
• ISSN: 0921-5093

Semi-solid metal processing involves processing metallic alloys between the solidus and the liquidus. The microstructure must be non-dendritic and consist of spheroids of solid in a liquid matrix. Two potential routes to suitable starting material are recrystallisation and partial melting (RAP) and cooling slope (CS). Here the microstructural coarsening of such materials in the semi-solid state is compared with rates in the literature. A slightly lower coarsening rate was observed for RAP route 2014 alloy with 37% fraction liquid than for CS route 2014 alloy with 17% fraction liquid despite the higher fraction liquid for the former. For the CS route, an increase in fraction liquid gave a higher coarsening rate. A relatively high coarsening rate was observed in a modified 2014 alloy with the Fe, Mn and Zn stripped out of the composition and a relatively low Si content. The coarsening rate was also relatively high for alloy 201 prepared by the CS route compared with alloy 2014 either by RAP or CS. It is likely that relatively low coarsening rates are associated with the presence of particles which are inhibiting the migration of liquid film grain boundaries, either through a pinning mechanism or through impeding diffusion through the liquid film at the boundary.