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Title: On Delamination Toughening of a 14YWT Nanostructured Ferritic Alloy

The FCRD NFA-1 is a high strength, irradiation tolerant nanostructured ferritic alloy (NFA) produced by ball milling argon atomized Fe-14Cr-3W-0.35Ti-0.25Y (wt.%) and FeO powders, followed by hot extrusion at 850 °C, and subsequent annealing and cross-rolling at 1000 °C. The microstructure of the resulting ≈10 mm thick NFA-1 plate is dominated by ultrafine sub-micron pancake shaped grains, and a large population of microcracks lying on planes parallel to the plate faces. Pre-cracked fracture toughness tests in four different orientations (L-T, T-L, L-S and T-S) show stable crack growth by ductile tearing, with peak load K Jc from ≈ 88 to 154 MPa√m at ambient temperature. Stable crack tearing persists down to ≈ -175 °C and is accompanied by extensive delamination due to the propagation of the microcracks. Depending on the specimen orientation, this unusual toughening mechanism is either due to a reduction of crack tip stresses in thin ligaments formed by the delaminations (L-T and T-L), or 90° deflection of cracks initially running normal to the delaminations (L-S and T-S), thereby suppressing cleavage in both cases. Lastly, understanding the fracture processes in NFA-1 is also important to its irradiation tolerance in nuclear service as well as its fabricability in makingmore » defect-free components such as thin-walled tubing.« less
Authors:
 [1] ;  [1] ; ORCiD logo [2] ;  [1]
  1. Univ. of California, Santa Barbara, CA (United States). Materials Dept.
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-18-22328
Journal ID: ISSN 1359-6454
Grant/Contract Number:
AC52-06NA25396; FG03-94ER54275
Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 136; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Nanostructured ferritic alloy; ODS ferritic steel; Texture; Delamination; Fracture toughness
OSTI Identifier:
1455000