Microstructural Stability and Rheological Behavior of Al-Si-Cu Alloys in the Semi-solid State

Author(s)

Torres, Luis Vanderlei ; Zoqui, Eugenio Jose

• Document type: Journal article
• Source: METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE; v. 53, n. 5, p. 17-pg., 2022-08-10.

Abstract

This study investigates the microstructural stability and consequent rheological behavior of Al-Si-Cu in the semi-solid state. It covers different stages in the production of the alloy, characterization of the microstructure in the as-cast condition and the effect of reheating to a semi-solid slurry on the microstructure and viscous behavior. Al3Si2.5Cu, Al5Si2.5Cu, and Al7Si2.5Cu alloys were produced by conventional casting with intense electromagnetic stirring. The alloys were then reheated to temperatures corresponding to 45 and 60 pct, solid fractions and held at these temperatures for 0, 30, 90 and 210 second to investigate spheroidization of the solid phase immersed in liquid. The best rheological behavior was achieved for alloys reheated to a 45 pct solid fraction, which had an apparent viscosity of around 1 Pa s, like glycerol, or even 10 Pa s, like honey, for strains of up to 65 pct. However, for strains of between 65 and 80 pct the viscosity increased rapidly to 10(4) to 10(5) Pa s. These values are similar to those for molten glass and are a result of the start of solid-solid interaction. Even with viscosities as high as these, all the alloys exhibited excellent formability in the semi-solid state regardless of their silicon content. (AU)

• FAPESP's process: 15/22143-3 - Fatigue behaviour of thixoformed alloys
• Grantee: Eugênio José Zoqui
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/11802-4 - Mechanical properties of new Al-Si-(Zn-Cu-Mg) aloys for rheocasting and thixoforming
• Grantee: Eugênio José Zoqui
• Support Opportunities: Regular Research Grants
• FAPESP's process: 09/08478-1 - Continuous Casting and Thixoforming of new Al-Si-Cu-Mg alloys
• Grantee: Luis Vanderlei Torres
• Support Opportunities: Scholarships in Brazil - Doctorate