Abstract
Primary grain refinement using inoculant additions and intermetallic compound (IMC) phase selection are critical aspects in the solidification of commercial aluminum alloys, controlling the final mechanical properties in service. Although there have been studies which suggest there are explicit interactions between the two phenomena, they have yet to be fully elucidated. Here, through study of intermetallic phase particles extracted from an inoculated casting, key features relating to the nucleation of different intermetallic phases via eutectic reactions are recognized and explained. In particular, rake-like IMCs are identified as initiation points for the deleterious beta -AlFeSi IMC phase in a model 6xxx series Al alloy. A mechanism is proposed for how {text{TiB}}_{2} inoculant particles, which are commonly used for primary phase refinement, play a role in enhancing the nucleation of intermetallic phases during eutectic reactions at the liquid/alpha -Al interface in the final stages of solidification. The implication of this mechanism is that, after the event of primary grain refinement, any unused {text{TiB}}_{2} inoculant particles could be contributing to IMC formation thereby affecting the overall type, size, and distribution of intermetallic phases in the solidified alloy.
Highlights
INTERMETALLIC phases form towards the latter stages of solidification in aluminum alloys from the interaction of solute atoms, which are rejected from the growing, relatively dilute, primary a-Al grains and have become concentrated in the shrinking fraction of intergranular liquid
Phase identification of the extracted particles using X-ray diffraction (XRD) suggested that the noninoculated alloy contained predominantly ac-AlFeSi (Figure 2(a)) whereas the extracted particles from the inoculated samples consist of mostly b-AlFeSi (Figure 2(b))
Microstructural features have been identified as the initiation points for b-AlFeSi intermetallic compound (IMC) particle formation using extraction from an inoculated aluminum casting, and clusters of TiB2 grain refiner particles were commonly colocated with the same particular IMC features
Summary
INTERMETALLIC phases form towards the latter stages of solidification in aluminum alloys from the interaction of solute atoms, which are rejected from the growing, relatively dilute, primary a-Al grains (crystals) and have become concentrated in the shrinking fraction of intergranular liquid. The type, size, and distribution of these intermetallic phases have considerable influence on the final properties of commercial aluminum alloys, and are arguably more important than the size and morphology of primary a-Al grains, which are in any case often recrystallized during downstream processing. One of the most important class of intermetallic phases are those based on AlFeSi. In 6xxx series (dilute Al-Si-Fe-Mg) alloys, metastable cubic Al8Fe2Si and monoclinic Al5FeSi, designated as ac-AlFeSi and b-AlFeSi respectively, form by late stage, high solid fraction solidification reactions[2,3] such as:
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
