J. Phys. Colloques
Volume 48, Numéro C3, Septembre 19874th International Aluminium Lithium Conference
|Page(s)||C3-685 - C3-691|
J. Phys. Colloques 48 (1987) C3-685-C3-691
THE EFFECT OF LOW MELTING POINT IMPURITIES ON THE PROPERTIES OF Al-Li ALLOYSD. WEBSTER
Kaiser Aluminum and Chemical Corporation, P.O. Box 877, Pleasanton, CA 94566, U.S.A.
The effect of low melting point impurities, such as sodium and potassium, on the properties and microstructure of Al-Li alloys has been investigated. These impurities have been shown to occur as discret lenticular particles along grain boundaries. In underaged and peak-aged conditions, the impurity particles are liquid and the toughness and ductility of alloys in this condition were found to be improved by lowering the test temperature below the freezing point of the impurity. In the overaged condition, the sodium and potassium occur as a solid phase and materials in this condition were found to follow the pattern of most aluminum alloys and show a decrease in Charpy impact toughness as the testing temperature was lowered. The addition of sodium and potassium to Al-Li alloys reduced toughness and ductility at room temperature in the range of compositions investigated (up to 476 ppm Na and up to 23 ppm K). Low melting point impurities were found to have little effect on the toughness or ductility of high purity aluminum.