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Open AccessArticle

Grain Refinement Effect on the Hot-Tearing Resistance of Higher-Temperature Al–Cu–Mn–Zr Alloys

1
Computational Sciences & Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
2
Metallurgical and Materials Engineering Department, Colorado School of Mines, Golden, CO 80401, USA
3
Fiat Chrysler Automobiles North America, LLC., Auburn Hills, MI 48326, USA
4
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
5
Nemak Monterrey, 66000 Garcia Monterrey, Mexico
*
Author to whom correspondence should be addressed.
Metals 2020, 10(4), 430; https://doi.org/10.3390/met10040430
Received: 9 March 2020 / Revised: 20 March 2020 / Accepted: 23 March 2020 / Published: 25 March 2020
(This article belongs to the Special Issue Dedicating to Professor John Campbell's 80th Birthday)
The hot-tearing resistance of Al-Cu-Mn-Zr (ACMZ) alloys was investigated as a step toward introducing these new cast alloys for severe duty, higher-temperature applications, such as cylinder heads for down-sized, turbocharged automotive engines. Alloy Cu compositions were varied from 5 to 8 wt.%. Targeted Ti levels were 0.02, 0.1, and 0.2 wt.% via additions of the Al–5Ti–1B master alloy. Hot-tearing resistance was assessed by visual examination and ranking of the cracking severity in a multi-arm permanent mold casting. It was found that at high impurity contents (Fe and Si of 0.2 wt.% each), the Al–Cu–Mn–Zr alloy with 4.95 wt.% Cu exhibited the poorest hot-tearing resistance, irrespective of the grain refining amount. Microstructural analysis indicated an effective reduction in the grain size, as the Ti additions were increased to 0.02 and 0.1 wt.% Ti via the Al–Ti–B grain refiner. The finest grain size was attained with a 0.1 wt.% Ti. Based on the hot-tearing evaluation, it was found that the additional grain refining via the Al–5Ti–1B master alloy at 0.1 wt.% Ti significantly reduces the hot-tearing susceptibility at Cu contents greater than 7.3 wt.% for ACMZ alloys with low Fe and Si. These findings indicate that the best hot-tearing resistance was observed at a grain refiner level of 0.1 wt.% Ti and high Cu content (greater than 7.3 wt.%). This study to indicates that these Al–Cu–Mn–Zr alloys, which possess excellent microstructural stability and mechanical properties at elevated temperatures, can also possess excellent hot-tearing resistance. View Full-Text
Keywords: casting; hot-tearing; aluminum; Al-Cu alloys casting; hot-tearing; aluminum; Al-Cu alloys
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MDPI and ACS Style

Sabau, A.S.; Milligan, B.K.; Mirmiran, S.; Glaspie, C.; Shyam, A.; Haynes, J.A.; Rodriguez, A.F.; Gonzales Villarreal, J.; Talamantes, J. Grain Refinement Effect on the Hot-Tearing Resistance of Higher-Temperature Al–Cu–Mn–Zr Alloys. Metals 2020, 10, 430.

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