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Open AccessArticle

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

Computational Sciences & Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
Metallurgical and Materials Engineering Department, Colorado School of Mines, Golden, CO 80401, USA
Fiat Chrysler Automobiles North America, LLC., Auburn Hills, MI 48326, USA
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
Nemak Monterrey, 66000 Garcia Monterrey, Mexico
Author to whom correspondence should be addressed.
Metals 2020, 10(4), 430;
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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