TEMPERATURE AND STRAIN-RATE DEPENDENCE OF THE PORTEVIN-LE CHATELIER EFFECT IN A RAPIDLY SOLIDIFIED AL-ALLOY

The Portevin-Le Chatelier (PL) effect was studied for a rapidly solidified aluminum alloy in a temperature range of 193 to 423 K and a strain rate range of 10(-5) to 10(-1) s(-1). Emphasis was put on the dependence of the critical strain (epsilon(c)) for the PL effect on temperature (T) and strain rate (epsilon). It is found that the overall epsilon(c)-T-epsilon relation is grouped into two categories: epsilon(c) increases with increasing epsilon but with decreasing T in the low T/high epsilon regime and epsilon(c) increases with increasing T but with decreasing epsilon in the high T/low epsilon regime. The underlying dynamic strain aging (DSA) mechanism is discussed to account for the two different yet unified categories by calculating activation energies and by introducing the transition conditions.