Activation Energy Calculations for the Portevin-Le Chatelier Effect in Nimonic 263 Superalloy

摘要

The Portevin-Le Chatelier (PLC) effect in the Nimonic 263 superalloy was investigated by tensile test in a wide temperature range, from room temperature to 1033 K (760 A degrees C), and at strain rates between 0.1 and 4 x 10(-4) s(-1). Types A, B, and C serrations were observed depending upon the test temperatures and strain rates. The activation energy (Q) for serrated flow was determined by employing various methodologies for T < 723 K (450 A degrees C), where a normal PLC effect was observed. The value of Q was found to be independent of the method employed. The average Q value of 70 KJ/mol was found to be in agreement with that for diffusion of substitutional solutes such as Cr and Mo in a Ni matrix by pipe diffusion. At temperatures ranging from 723 K to 923 K (450 A degrees C to 650 A degrees C), type C serrations and an inverse PLC effect were noticed, which may be caused by unlocking process.