About this Abstract |
Meeting |
Superalloys 2024
|
Symposium
|
Superalloys 2024
|
Presentation Title |
B-9: The PLC Effect in the Absence of Long-range Cottrell Atmospheres in RR1000 |
Author(s) |
Bradley Rowlands, James R Miller, Lewis R Owen, Howard J Stone, Wenwen Song, Xiao Shen, Enrique I Galindo-Nava, Cathie M Rae |
On-Site Speaker (Planned) |
Bradley Rowlands |
Abstract Scope |
The Portevin-Le Chatelier (PLC) effect is widely attributed to the partitioning of interstitial C atoms around dislocation cores in mild steels, to form Cottrell atmospheres. However, limited empirical evidence exists to clarify how similar mechanisms extend to complex multicomponent alloy systems such as Ni-based superalloys. The presence of the PLC effect was demonstrated in coarse-grained RR1000 from 200 °C – 550 °C through digital image correlation (DIC). The effect was also demonstrated in simple binary Ni-(20-25)Cr (wt. %) alloys, suggesting that the microstructural complexity of superalloys is not key to elucidating the atomistic origins. Probe-corrected scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectroscopy and atom probe tomography were performed on interrupted specimens displaying the PLC effect. No evidence of long-range solute enrichment was observed in the vicinity of dislocation cores. Hence, alternative origins for the effect were considered; evidence for short-range order was assessed in Ni-Cr powder through neutron diffraction. A preference was observed for particular local configurations of Ni and Cr atoms within a unit cell, resembling, but not identical to, those in long-range ordered Ni2Cr. High resolution STEM imaging demonstrated the presence of nanodomains in Ni-Cr and RR1000 containing diffraction contrast effects resembling superlattice fringes. STEM image simulations based on refined unit cell structures demonstrated that such features may relate to the local lattice distortion in short-range ordered (SRO) domains. The results do not support the presence of long-range Cottrell atmospheres within the temperature range of the PLC effect, but instead of SRO, an alternate hypothesised origin of the PLC effect. |
Proceedings Inclusion? |
Definite: At-meeting proceedings |