Structural evolution of rapidly solidified Al-Mn and Al-Mn-Sr alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 428; no. 1-2; pp. 188 - 195
• Main Authors: Vojtech, D, Saksl, K, Verner, J, Bartova, B
• Format: Journal Article
• Language: English
• Published: 25.07.2006
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2006.05.017

In the present paper, microstructure, phase composition and elevated temperature behaviour of two rapidly solidified (RS) Al-5.0 wt.% Mn and Al-4.6 wt.% Mn-2.1 wt.% Sr melt spun ribbons are described. The RS binary alloy was composed of supersaturated alpha-Al solid solution and finely dispersed spheroids of quasi-crystalline icosahedral I-Al6Mn phase. The Sr-addition led to a reduction of volume fraction of the I-Al6Mn phase. Manganese was more concentrated in stable tetragonal beta-Al4Sr phase. DSC measurements revealed exothermal reactions between 400 and 500 deg C which were more pronounced in the binary Al-Mn alloy. This proved a higher degree of metastability of the binary alloy. The solid state phase transformations included: 1. Decomposition of the supersaturated alpha-Al solid solution. 2. Polymorphous transformation of the quasi-crystalline icosahedral I-Al6Mn phase to a stable orthorhombic O-Al6Mn phase. The decomposition of the supersaturated solid solution produced finely dispersed O-Al6Mn precipitates which induced some hardening of both alloys after pre-annealing at 350 deg C/5 h.