Microstructure and Hardness of an Al-8 wt%Si-2.5 wt%Bi Alloy Subjected to Solidification Cooling Rates from 0.1 to 800 K s(-1)

Author(s)

Dias, Marcelino ; Bogno, Abdoul Aziz ; Spinelli, Jose Eduardo ; Oliveira, Ricardo ; Cheung, Noe ; Garcia, Amauri ; Henein, Hani

• Document type: Journal article
• Source: ADVANCED ENGINEERING MATERIALS; v. N/A, p. 11-pg., 2022-11-29.

Abstract

This work explores the effect of the addition of bismuth (Bi) to Al-8 wt%Si alloys. Bi in Aluminum based alloys works as a self-lubricating agent, improving machining and wear properties. As Bi is a soft material, it is essential to evaluate how it affects microstructural features and the resulting properties of Al-8 wt%Si alloys. Herein, this hypoeutectic alloy is modified by the addition of 2.5 wt%Bi and subjected to three solidification techniques: differential scanning calorimetry, transient directional solidification, and impulse atomization. Thus, this work investigates the effect of Bi in samples solidified under a wide range of cooling rates. Of specific interest is how Bi modifies the eutectic silicon morphology and alloy hardness compared with a hypoeutectic Al-10 wt%Si alloy from the literature. The silicon (Si) morphology of Al-8 wt%Si-2.5 wt%Bi transitions from flaky (coarse) to fibrous (fine) at a critical cooling rate of 1100 K s(-1). Through the combination of Bi addition and processing through impulse atomization, the ternary Al-Si-Bi alloy achieves improvements in hardness of up to 20% compared to Al-10 wt%Si. This is despite having a coarser eutectic microstructure than the binary hypoeutectic Al-Si alloy. This is due to Bi modifying the morphology of the eutectic Si. (AU)

• FAPESP's process: 16/18186-1 - Microstructural evolution and mechanical and wear resistances of ternary Al-Bi-Si and Al-Bi-Ni alloys unidirectionally solidified
• Grantee: José Marcelino da Silva Dias Filho
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 19/23673-7 - Evaluation of alloys for thermal interface contact and for additive manufacturing
• Grantee: José Eduardo Spinelli
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/11791-2 - Microstructural Evolution and Mechanical and Wear Resistances of Ternary Al-Bi-Si and Al-Bi-Ni alloys Unidirectionally Solidified
• Grantee: José Marcelino da Silva Dias Filho
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 17/12741-6 - Application of experimental solidification techniques, characterization of microstructure and properties in the evaluation of eutectic and hypereutectic Al-base and Zn-base alloys
• Grantee: José Eduardo Spinelli
• Support Opportunities: Regular Research Grants
• FAPESP's process: 17/15158-0 - Characterization of microstructure and properties in the evaluation of alloys for thermal interface contact
• Grantee: Amauri Garcia
• Support Opportunities: Regular Research Grants