Abstract
The Portevin-Le Chatelier (PLC) effect has been studied in the Ni-based superalloy IN100 which is currently used as a disk material in jet engines. A series of tensile tests was carried out at 588 K, 755 K, and 922 K (315 °C, 482 °C, and 649 °C) at plastic strain rates ranging from a low of 6.21 × 10−6 s−1 to a high of 4.92 × 10−2 s−1. The activation energy was determined using the slope of a line on a strain rate/temperature graph which divided the area of the graph into two regions: (1) “PLC behavior observed,” and (2) “No PLC behavior observed.” A new statistical approach was developed to objectively differentiate between a true PLC effect and experimental uncertainty (i.e., “noise”). The value of the activation energy was found to be 1.14 eV/atom, which strongly suggests that the rate controlling process was bulk diffusion of C in the lattice. A qualitative model, based on the Orowan equation and slip band dislocation mechanics, was proposed, which unifies the seemingly disparate ideas of the process being controlled by a single atom/dislocation interaction while at the same time exhibiting significant strains during PLC load drops.
| Original language | English |
|---|---|
| Pages (from-to) | 5596-5609 |
| Number of pages | 14 |
| Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
| Volume | 46 |
| Issue number | 12 |
| DOIs | |
| State | Published - Sep 21 2015 |
| Externally published | Yes |
Funding
We gratefully acknowledge materials and financial support received from Pratt and Whitney which made this research possible. We especially acknowledge very useful discussions with Dr. Alexander Staroselsky of United Technologies Research Center, Prof. R.W. Armstrong of the University of Maryland, Prof. Samuel Forest of Ecole des Mines (Paris), Prof. David McDowell of Georgia Tech, Prof. Hussein Zbib of Washington State University and with Prof. David Field of Washington State University.