Tetsuyuki Ikeda1 and Seiki Nishi2
1Graduate School, Nagoya University, Nagoya
The precipitation process in a supersaturated Al-3%Mn alloy solidified rapidly from the liquid state is very complex and it has been recognized that Al6Mn, G, G' and G'' phases are its decomposition products. Further, impurity elements iron and silicon have significant effect on the precipitation process of precipitating phases containing manganese. Accordingly, using Al-3%Mn alloy, the phase decomposition process of its supersaturated solid solution were examined. The experimental methods used were measurements of hardness and lattice parameter, and analyses by X-ray diffraction and EPMA. The results obtained were as follows:
(1) Considerable age-hardening of the supersaturated solid solution was induced by heating for a long time at 325∼350°C.
(2) At aging temperatures below 550°C, precipitating phases containing manganese were G, G' and G'' phases and, above 550°C, Al6Mn and G' phase.
(3) Impurity elements iron and silicon precipitated as the Al-Fe binary compounds or the ternary compounds and these phases had a significant effect on the nucleation and growth speed of the precipitating phases containing manganese.
(4) The variation in lattice parameter during isothermal heating was of the continuous type, but the lattice parameter was separated into two values in the early and middle stages of the precipitation process.
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