CHANGES IN MICROSTRUCTURES OF AL-5, 10-MA SS-PERCENT-MG BINARY-ALLOYSWITH AGING TREATMENT

Aluminum-magnesium alloys containing 5 and 10 mass%Mg were aged at tem peratures between 373 and 573 K for a prolonged time in order to inves tigate the precipitation process of the beta-phase and the variation i n solute Mg concentration in the matrix. The precipitates were examine d by means of X-ray diffraction, EPMA and differential scanning calori metry. The Mg concentration in the matrix was estimated using the elec trical resistivities measured at 77 and 300 K. The obtained results ar e summarized as follows. (1) Based on the variation in the solute Mg c oncentration of the matrix, the nose temperatures for the precipitatio ns of beta and/or beta'-phases were estimated to be about 453 and 493 K for 5%Mg and 10%Mg alloys. (2) The particle like precipitate was sug gested to be the stable precipitate beta-phase(Al3Mg2) from both X-ray diffraction and EPMA analyses. (3) In the Al-10%Mg alloy aged at 453 K, rod-like precipitates were found to have a coherent strain field ca used by the partially coherent interface with the matrix in the early stage of aging.