Mechanism of the Mg3Bi2 Phase Formation in Pb-Free Aluminum 6xxx Alloy with Bismuth Addition

• Published in: Crystals (Basel) Vol. 11; no. 4; p. 424
• Main Authors: Rečnik, Simon, Bizjak, Milan, Medved, Jožef, Cvahte, Peter, Karpe, Blaž, Nagode, Aleš
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-04-2021
• Subjects: Alloys; Aluminum alloys; Aluminum base alloys; Bismuth; Cutting tools; Ductility; Equilibrium; free-machining AA6xxx alloy; Grain refinement; Grain size; Holding furnaces; Induction melting; Laboratories; Lead free; Machinability; Melt temperature; Melting furnaces; Methods; Mg3Bi2 phase; Microstructure; Potassium; Productivity; Software; Solidification; solidification model; Germany; Slovenia
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst11040424

In the present work, free-cutting aluminum alloy AA6026 with 1.1 wt.% bismuth addition was fabricated by different melt preparation methods in order to investigate whether the melt preparation route affects the solidification sequence and thus has an influence on the machinability of the alloy. All experiments were designed to simulate variable industrial conditions: addition of bismuth in an induction melting furnace, addition of bismuth in an electric resistance holding furnace, addition of bismuth together with grain refiner, effect of holding time and melt temperature before casting. Detailed thermodynamic analyses (DSC, Thermo-Calc) and microstructural characterization (SEM-EDS, XRD) have been performed to explain the solidification sequence, microstructure development and especially formation of the intermetallic Mg3Bi2 phase.