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 solidi fied aluminum alloy in a temperature range of 193 to 423 K and a strai n rate range of 10(-5) to 10(-1) s(-1). Emphasis was put on the depend ence of the critical strain (epsilon(c)) for the PL effect on temperat ure (T) and strain rate (epsilon). It is found that the overall epsilo n(c)-T-epsilon relation is grouped into two categories: epsilon(c) inc reases with increasing epsilon but with decreasing T in the low T/high epsilon regime and epsilon(c) increases with increasing T but with de creasing epsilon in the high T/low epsilon regime. The underlying dyna mic strain aging (DSA) mechanism is discussed to account for the two d ifferent yet unified categories by calculating activation energies and by introducing the transition conditions.