Effects of mischmetal composition and cooling rates on the microstructure and mechanical properties of Al-(Ce, La, Nd) eutectic alloys

Jie Qi; Erin C. Bryan; David C. Dunand

doi:10.1016/j.msea.2025.147912

Effects of mischmetal composition and cooling rates on the microstructure and mechanical properties of Al-(Ce, La, Nd) eutectic alloys

Jie Qi^*, Erin C. Bryan, David C. Dunand

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

Abstract

This study investigates the substitution of cerium (Ce) with mischmetal (MM) in cast Al-MM alloys, focusing on microstructure, hardness, tensile/compression properties, creep resistance, and coarsening resistance. Al-MM alloys with various MM compositions (Ce, Ce-50La, Ce-33La, and Ce-27La-19Nd, wt%) exhibit near-eutectic and hyper-eutectic microstructures for Al-9MM and Al-12MM compositions, respectively, with similar as-cast hardness (∼525 MPa). All Al-9MM alloys show tensile yield stress ∼55 MPa, ultimate tensile strength ∼130 MPa, and fracture strain ∼8 %. The microstructural and mechanical properties consistency demonstrates the flexibility of MM compositions in Al-MM alloys. Al-9MM exhibits excellent coarsening resistance, with minimal hardness reduction when exposed to 300 and 350 °C for up to 11 weeks, and a modest ∼15 % hardness reduction at 400 °C for 8 weeks, outperforming eutectic Al-12.6Si and Al-6.4Ni alloys. Additionally, Al-9MM shows higher creep resistance at 300 °C compared to most precipitate-strengthened Al-Sc-Zr and solid-solution-strengthened Al-Mg/Mn alloys, but is outperformed by eutectic-strengthened Al-6.4Ni and Al-10Ce-5Ni alloys. The effect of casting cooling rate is investigated through wedge casting: Al-9Ce transitions from hypo-to hyper-eutectic as cooling rates decrease, while Al-12Ce consistently shows hyper-eutectic microstructures. Al₁₁Ce₃ lamellae become finer and more closely spaced with increasing cooling rates. Al-9Ce maintains steady hardness at high to moderate cooling rates but shows reduced hardness at lower rates, whereas Al-12Ce shows no change in hardness. With a 15 % reduction in energy consumption and CO₂ emissions, Al-Ce alloys where Ce is replaced with MM offer comparable mechanical properties and enhanced environmental benefits, highlighting MM's potential as a sustainable alternative.

Original language	English (US)
Article number	147912
Journal	Materials Science and Engineering: A
Volume	925
DOIs	https://doi.org/10.1016/j.msea.2025.147912
State	Published - Mar 2025

Funding

This research was sponsored by award DE-EE0010221 under the Advanced Materials and Manufacturing Technologies Office, Office of Energy Efficiency and Renewable Energy, the U.S. Department of Energy. Specimen preparation by arc melting was performed at the Northwestern University Center for Atom Probe Tomography (NUCAPT). NUCAPT received support from the MRSEC program (NSF DMR-2308691) at the Materials Research Center, the SHyNE Resource (NSF ECCS-2025633), and the Paula M. Trienens Institute for Sustainability and Energy at Northwestern University. This work made use of the EPIC facility of Northwestern University's NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern's MRSEC program (NSF DMR-1720139). The authors thank (i) Mr. David Weiss (Eck Industries, WI) and Mr. Scott Rose (Boeing Research & Technology) for numerous useful discussions; (ii) Prof. Xiaohan Du (City University of Hong Kong) for her assistance in FEM modeling; (iii) Ms. Katalin Maji (Evanston Township High School, IL) for her assistance in sample processing and hardness measurements and (iv) Dr. Clement N. Ekaputra (Northwestern University, IL) for his assistance in cooling rate measurements. This research was sponsored by award DE-EE0010221 under the Advanced Materials and Manufacturing Technologies Office, Office of Energy Efficiency and Renewable Energy, the U.S. Department of Energy. Specimen preparation by arc melting was performed at the Northwestern University Center for Atom Probe Tomography (NUCAPT). NUCAPT received support from the MRSEC program (NSF DMR-2308691) at the Materials Research Center, the SHyNE Resource (NSF ECCS-2025633), and the Paula M. Trienens Institute for Sustainability and Energy at Northwestern University. This work made use of the EPIC facility of Northwestern University\u2019s NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern\u2019s MRSEC program (NSF DMR-1720139). The authors thank (i) Mr. David Weiss (Eck Industries, WI) and Mr. Scott Rose (Boeing Research & Technology) for numerous useful discussions; (ii) Prof. Xiaohan Du (City University of Hong Kong) for her assistance in FEM modeling; (iii) Ms. Katalin Maji (Evanston Township High School, IL) for her assistance in sample processing and hardness measurements and (iv) Dr. Clement N. Ekaputra (Northwestern University, IL) for his assistance in cooling rate measurements.

ASJC Scopus subject areas

General Materials Science
Condensed Matter Physics
Mechanics of Materials
Mechanical Engineering

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title = "Effects of mischmetal composition and cooling rates on the microstructure and mechanical properties of Al-(Ce, La, Nd) eutectic alloys",

abstract = "This study investigates the substitution of cerium (Ce) with mischmetal (MM) in cast Al-MM alloys, focusing on microstructure, hardness, tensile/compression properties, creep resistance, and coarsening resistance. Al-MM alloys with various MM compositions (Ce, Ce-50La, Ce-33La, and Ce-27La-19Nd, wt%) exhibit near-eutectic and hyper-eutectic microstructures for Al-9MM and Al-12MM compositions, respectively, with similar as-cast hardness (∼525 MPa). All Al-9MM alloys show tensile yield stress ∼55 MPa, ultimate tensile strength ∼130 MPa, and fracture strain ∼8 %. The microstructural and mechanical properties consistency demonstrates the flexibility of MM compositions in Al-MM alloys. Al-9MM exhibits excellent coarsening resistance, with minimal hardness reduction when exposed to 300 and 350 °C for up to 11 weeks, and a modest ∼15 % hardness reduction at 400 °C for 8 weeks, outperforming eutectic Al-12.6Si and Al-6.4Ni alloys. Additionally, Al-9MM shows higher creep resistance at 300 °C compared to most precipitate-strengthened Al-Sc-Zr and solid-solution-strengthened Al-Mg/Mn alloys, but is outperformed by eutectic-strengthened Al-6.4Ni and Al-10Ce-5Ni alloys. The effect of casting cooling rate is investigated through wedge casting: Al-9Ce transitions from hypo-to hyper-eutectic as cooling rates decrease, while Al-12Ce consistently shows hyper-eutectic microstructures. Al11Ce3 lamellae become finer and more closely spaced with increasing cooling rates. Al-9Ce maintains steady hardness at high to moderate cooling rates but shows reduced hardness at lower rates, whereas Al-12Ce shows no change in hardness. With a 15 % reduction in energy consumption and CO2 emissions, Al-Ce alloys where Ce is replaced with MM offer comparable mechanical properties and enhanced environmental benefits, highlighting MM's potential as a sustainable alternative.",

author = "Jie Qi and Bryan, {Erin C.} and Dunand, {David C.}",

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year = "2025",

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doi = "10.1016/j.msea.2025.147912",

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T1 - Effects of mischmetal composition and cooling rates on the microstructure and mechanical properties of Al-(Ce, La, Nd) eutectic alloys

AU - Qi, Jie

AU - Bryan, Erin C.

AU - Dunand, David C.

PY - 2025/3

Y1 - 2025/3

N2 - This study investigates the substitution of cerium (Ce) with mischmetal (MM) in cast Al-MM alloys, focusing on microstructure, hardness, tensile/compression properties, creep resistance, and coarsening resistance. Al-MM alloys with various MM compositions (Ce, Ce-50La, Ce-33La, and Ce-27La-19Nd, wt%) exhibit near-eutectic and hyper-eutectic microstructures for Al-9MM and Al-12MM compositions, respectively, with similar as-cast hardness (∼525 MPa). All Al-9MM alloys show tensile yield stress ∼55 MPa, ultimate tensile strength ∼130 MPa, and fracture strain ∼8 %. The microstructural and mechanical properties consistency demonstrates the flexibility of MM compositions in Al-MM alloys. Al-9MM exhibits excellent coarsening resistance, with minimal hardness reduction when exposed to 300 and 350 °C for up to 11 weeks, and a modest ∼15 % hardness reduction at 400 °C for 8 weeks, outperforming eutectic Al-12.6Si and Al-6.4Ni alloys. Additionally, Al-9MM shows higher creep resistance at 300 °C compared to most precipitate-strengthened Al-Sc-Zr and solid-solution-strengthened Al-Mg/Mn alloys, but is outperformed by eutectic-strengthened Al-6.4Ni and Al-10Ce-5Ni alloys. The effect of casting cooling rate is investigated through wedge casting: Al-9Ce transitions from hypo-to hyper-eutectic as cooling rates decrease, while Al-12Ce consistently shows hyper-eutectic microstructures. Al11Ce3 lamellae become finer and more closely spaced with increasing cooling rates. Al-9Ce maintains steady hardness at high to moderate cooling rates but shows reduced hardness at lower rates, whereas Al-12Ce shows no change in hardness. With a 15 % reduction in energy consumption and CO2 emissions, Al-Ce alloys where Ce is replaced with MM offer comparable mechanical properties and enhanced environmental benefits, highlighting MM's potential as a sustainable alternative.

AB - This study investigates the substitution of cerium (Ce) with mischmetal (MM) in cast Al-MM alloys, focusing on microstructure, hardness, tensile/compression properties, creep resistance, and coarsening resistance. Al-MM alloys with various MM compositions (Ce, Ce-50La, Ce-33La, and Ce-27La-19Nd, wt%) exhibit near-eutectic and hyper-eutectic microstructures for Al-9MM and Al-12MM compositions, respectively, with similar as-cast hardness (∼525 MPa). All Al-9MM alloys show tensile yield stress ∼55 MPa, ultimate tensile strength ∼130 MPa, and fracture strain ∼8 %. The microstructural and mechanical properties consistency demonstrates the flexibility of MM compositions in Al-MM alloys. Al-9MM exhibits excellent coarsening resistance, with minimal hardness reduction when exposed to 300 and 350 °C for up to 11 weeks, and a modest ∼15 % hardness reduction at 400 °C for 8 weeks, outperforming eutectic Al-12.6Si and Al-6.4Ni alloys. Additionally, Al-9MM shows higher creep resistance at 300 °C compared to most precipitate-strengthened Al-Sc-Zr and solid-solution-strengthened Al-Mg/Mn alloys, but is outperformed by eutectic-strengthened Al-6.4Ni and Al-10Ce-5Ni alloys. The effect of casting cooling rate is investigated through wedge casting: Al-9Ce transitions from hypo-to hyper-eutectic as cooling rates decrease, while Al-12Ce consistently shows hyper-eutectic microstructures. Al11Ce3 lamellae become finer and more closely spaced with increasing cooling rates. Al-9Ce maintains steady hardness at high to moderate cooling rates but shows reduced hardness at lower rates, whereas Al-12Ce shows no change in hardness. With a 15 % reduction in energy consumption and CO2 emissions, Al-Ce alloys where Ce is replaced with MM offer comparable mechanical properties and enhanced environmental benefits, highlighting MM's potential as a sustainable alternative.

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Effects of mischmetal composition and cooling rates on the microstructure and mechanical properties of Al-(Ce, La, Nd) eutectic alloys

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