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

Abstract

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 making defect-freemore » components such as thin-walled tubing.« less

Authors:

Alam, M.E. ^[1]; Pal, S. ^[1]; Maloy, Stuart Andrew  ^[2];

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Odette, G.R. ^[1]

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+ Show Author Affiliations

1. Univ. of California, Santa Barbara, CA (United States). Materials Dept.
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Publication Date:

Thu Jun 22 00:00:00 EDT 2017

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

National Science Foundation (NSF); USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Nuclear Energy (NE), Nuclear Fuel Cycle and Supply Chain

OSTI Identifier:

1455000

Alternate Identifier(s):

OSTI ID: 1550181

Report Number(s):

LA-UR-18-22328
Journal ID: ISSN 1359-6454; TRN: US1901189

Grant/Contract Number:  

AC52-06NA25396; FG03-94ER54275; 00119430 8-442520-59048; LANL8-442550-59434

Resource Type:

Accepted Manuscript

Journal Name:

Acta Materialia

Additional Journal Information:

Journal Volume: 136; Journal ID: ISSN 1359-6454

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Nanostructured ferritic alloy; ODS ferritic steel; Texture; Delamination; Fracture toughness