Decomposition characteristics of Al-Mn-Zr alloys rapidly-quenched from the melt
Abstract
The rapidly-quenched structures of liquid Al-Mn-Zr ternary alloys and Al-Mn binary alloys and their decomposition behaviors were investigated by hardness tests, X-ray diffraction analyses, and TEM observations. The solid solubility of Mn can be extended to about 10 wt pct irrespective of whether the alloys contain 1 wt pct Zr or not. The solidification structures are composed of fine dendritic cells and with increasing Mn content, interdendritic precipitates gather volume and branch out into the cell grains. The decomposition of rapidly-quenched alloys takes place during aging for 1 hour at temperatures of 300 to 350 °C, and the dependence of the decomposition temperatures on the Mn content varies in this range. Precipitation hardening of the ternary alloys is intensified by the addition of Mn up to about 7 wt pct and proceeds in a two-step manner during aging in the temperature range examined (350 to 450 °C). It is suggested that the precipitates contributing to the maximum hardening are pseudomorphous to the Al6Mn equilibrium phase.
- Publication:
-
Metallurgical Transactions A
- Pub Date:
- May 1986
- DOI:
- 10.1007/BF02643855
- Bibcode:
- 1986MTA....17..799O