Tetsuyuki Ikeda1, Seiki Nishi2 and Hiroshi Seo3
1Graduate School, Nagoya University, Nagoya
By rapid cooling of Al-1∼5%Mn alloys from the liquid state, solidified structures showed remarkable changes with cooling rate. By lattice parameter measurements and analyses of X-ray diffraction and EPMA line-scanning patterns, the solid solubility of manganese in the matrix, crystallized compound phase in those structures and the structure distribution were examined. The results obtained were as follows:
(1) With increase in solidification rate, the lattice parameters of matrix phases decreased from 4.045 Å to the value corresponding to complete supersaturation according to the degree of supersaturation in the range of solidification rate with the occurrence of incompletely supersaturated solid solution. Other structures showed constant lattice parameters.
(2) The conditions for formation of supersaturated solid solutions and the distribution diagram of solidified structures were determined from the change of the lattice parameter.
(3) In incompletely supersaturated solid solution, a new metastable intermediate phase AlmMn (simple cubic, a0=12.727 Å) and an equilibrium phase Al6Mn were crystallized. The structure produced by the movement of the eutectic point and an equilibrium structure was Al6Mn (or Al6(Mn, Fe)). Furthermore, compound phases containing impurity elements of iron or silicon (Al6Fe, Al3Fe, α -Al12Mn3Si and α -Al-Fe-Si) were detected in those structures.
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