Formation and morphological development of porosity in icosahedral Al-Pd-Mn alloys

Directional solidification and quenching experiments have been conducted to examine the formation and origin of the faceted porosity commonly observed in icosahedral Al-Pd-Mn alloys. Faceted porosity has been previously obser ved in both Czochralski grown and Bridgman grown single crystals during sin gle-phase solidification of the icosahedral phase. Detailed observations in Bridgman grown single crystals indicate that the distribution and quantity of pores are non-uniformly distributed along the length of the as-grown in got. This non-uniform distribution suggests that their formation is influen ced by both chemical segregation during solidification as well as convectio n in the liquid. Controlled solidification of this alloy followed by quench ing of the solid-liquid interface provides for a time-temperature history o f the porosity formation and morphological development as a function of pro cessing conditions. (C) 2000 Elsevier Science B.V. All rights reserved.