Effects of the third element on creep behavior of Al-Mg and αFe-Be solid solution alloys

In creep of alpha-iron, IS effects (interstitial-substitutional interaction) were reported. Similar effects are expected in ternary substitutional solid solutions. In the present report, effects of the second substitute (the third element), whose size misfit is small, on creep behavior and the transition stress from Alloy-type to Metal-type have been investigated experimentally. Three alloy systems are employed, i.e. aluminum-magnesium-zinc, aluminum-magnesium-lithium and alpha iron-beryllium-manganese solid solutions. Although no change in equivalent magnesium concentration by the addition of zinc nor lithium is expected, creep rates and the transition stress in Al-Mg alloys are affected by these third elements. Similar changes are observed in alpha iron-beryllium-manganese system. Substitutional elements are not always independent with each other, so that the apparent interaction between the first substitute, i.e. magnesium or beryllium, and a dislocation can be affected by the third elements.