Segregation-assisted plasticity in Ni-based superalloys

Journal article

Correlative high resolution transmission electron microscopy and energydispersive X-ray spectroscopy are used to study deformation-induced planar faults in the single crystal superalloy MD2 crept at 800 ◦C and 650 MPa. Segregation of Cr and Co at microtwins, anti-phase boundaries (APB) and complex/superlattice extrinsic and intrinsic stacking faults (CESF/SESF and CISF/SISF) is confirmed and quantified. The extent of this is found to depend upon the fault type, being most pronounced for the APB. The CESF/SESF is studied in detail due to its role as a precursor of the microtwins causing the majority of plasticity under these conditions. Quantitative modelling is carried out to rationalize the findings; the experimental results are consistent with a greater predicted velocity for the lengthening of the CESF/SESF – compared with the other types of fault – and hence confirm its role in the diffusion-assisted plasticity needed for the microtwinning mechanism to be operative

Authors: Barba Cancho, D; Smith, T; Miao, J; Mills, M; Reed, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer US
• Journal: Metallurgical and Materials Transactions A
• Volume: 49
• Issue: 9
• Pages: 4173–4185
• Publication date: 2018-03-26
• Acceptance date: 2018-03-05
• DOI: 10.1007/s11661-018-4567-6
• EISSN: 1543-1940
• ISSN: 1073-5623
• Keywords: diffusion; EDX; planar faults; phase transformation; Ni-based superalloy; STEM; creep plasticity; segregation