The mechanism of twin thickening and the elastic strain state of TWIP steel nanotwins

DOI: 10.1016/j.msea.2023.145005

Authors: Thomas W. J. Kwok (Imperial College London) , T. P. Mcauliffe (Imperial College London) , A. K. Ackerman (Imperial College London) , B. H. Savitzky (National Center for Electron Microscopy (NCEM) (USA)) , M. Danaie (Diamond Light Source) , C. Ophus (National Center for Electron Microscopy (NCEM) (USA)) , D. Dye (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Materials Science And Engineering: A , VOL 324

State: Published (Approved)
Published: April 2023
Diamond Proposal Number(s): 18770

Abstract: A Twinning Induced Plasticity (TWIP) steel with a nominal composition of Fe-16.4Mn-0.9C-0.5Si-0.05Nb-0.05V was deformed to an engineering strain of 6%. The strain around the deformation twins were mapped using the 4D-STEM technique. Strain mapping showed a large average elastic strain of approximately 6% in the directions parallel and perpendicular to the twinning direction. However, the large average strain comprised of several hot spots of even larger strains of up to 12%. These hot spots could be attributed to a high density of sessile Frank dislocations on the twin boundary and correspond to shear stresses of 1–1.5 GPa. The strain and therefore stress fields are significantly larger than other materials known to twin and are speculated to be responsible for the early thickness saturation of TWIP steel nanotwins. The ability to keep twins extremely thin helps improve grain fragmentation, i.e. the dynamic Hall-Petch effect, and underpins the large elongations and strain hardening rates in TWIP steels.

Journal Keywords: Twinning; 4D-STEM; TWIP steels; Scanning Transmission Electron Microscopy

Diamond Keywords: Alloys

Subject Areas: Materials, Engineering

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E02-JEM ARM 300CF

Added On: 12/04/2023 08:22

Documents:
1-s2.0-S092150932300429X-main.pdf

Discipline Tags:

Materials Engineering & Processes Materials Science Engineering & Technology Metallurgy

Technical Tags:

Microscopy Electron Microscopy (EM) Scanning Transmission Electron Microscopy (STEM)