, Volume 15, Issue 11, pp 1987-1997

Precipitation in rapidly solidified Al-Mn alloys

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Abstract

Precipitation at 450 °C was studied in melt-spun ribbons containing up to 15 wt pct Mn in solid solution in Al. The as-spun ribbons were microsegregation-free at compositions up to 5 wt pct Mn, but in more concentrated alloys a cellular microstructure was present. Upon annealing, four precipitate phases are observed, some of them being found preferentially on cell boundaries and others being found within the cells. Al6Mn, G, and the Gℍ phase can coexist for long times at 450 °C, but the G phase appears to be slightly more stable. A less stable T phase was detected in Al-5 wt pct Mn foils following short annealing periods. The supersaturation of the Al matrix can persist for many hours in alloys containing up to 3 wt pct Mn, but is essentially gone after 1 hour in alloys with 5 wt pct Mn or more.

On leave at the Center for Materials Research, The Johns Hopkins University, Baltimore, MD 21218. R.J.