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Title: Effect of tube processing methods on microstructure, mechanical properties and irradiation response of 14YWT nanostructured ferritic alloys

Abstract

In this research, innovative thermal spray deposition (Process I) and conventional hot extrusion processing (Process II) methods have been used to produce thin walled tubing (~0.5 mm wall thickness) out of 14YWT, a nanostructured ferritic alloy. The effects of processing methods on the microstructure, mechanical properties and irradiation response have been investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and, micro- and nano-hardness techniques. It has been found that these two processes have a significant effect on the microstructure and mechanical properties of the as-fabricated 14YWT tubes. Even though both processing methods yield the formation of various size Y-Ti-O particles, the conventional hot extrusion method results in a microstructure with smaller, homogenously distributed nano-oxides (NOs, Y-Ti-O particles < 5 nm) with higher density. Therefore, Process II tubes exhibit twice the hardness of Process I tubes. It has also been found that these two tremendously different initial microstructures strongly affect irradiation response in these tubes under extremely high dose ion irradiations up to 1100 peak dpa at 450 °C. The finer, denser and homogenously distributed NOs in the Process II tube result in a reduction in swelling by two orders of magnitude. On the other hand, inhomogeneity ofmore » the initial microstructure in the Process I tube leads to large variations in both swelling and irradiation induced hardening. Moreover, hardening mechanisms before and after irradiation were measured and compared with detailed calculations. In conclusion, this study clearly indicates the crucial effect of initial microstructure on radiation response of 14YWT alloys.« less

Authors:
 [1];  [1];  [2];  [3];  [4];  [4];  [4];  [5]; ORCiD logo [6]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of New Mexico, Albuquerque, NM (United States)
  3. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  4. Texas A & M Univ., College Station, TX (United States)
  5. Ames Lab., Ames, IA (United States)
  6. Case Western Reserve Univ., Cleveland, OH (United States)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE), Fuel Cycle Technologies (NE-5)
OSTI Identifier:
1407908
Alternate Identifier(s):
OSTI ID: 1379172
Report Number(s):
IS-J-9434; LA-UR-17-29321
Journal ID: ISSN 1359-6454; PII: S1359645417304408
Grant/Contract Number:
AC52-06NA25396; NE0008297; AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 134; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Nanostructured ferritic alloys (NFAs); Nano-oxides (NOs); Ion irradiation; Swelling; Hardening; nanostructured ferritic alloys (NFAs); nano-oxides (NOs); ion irradiation; swelling; hardening

Citation Formats

Aydogan, E., Maloy, S. A., Anderoglu, O., Sun, C., Gigax, J. G., Shao, L., Garner, F. A., Anderson, I. E., and Lewandowski, J. J. Effect of tube processing methods on microstructure, mechanical properties and irradiation response of 14YWT nanostructured ferritic alloys. United States: N. p., 2017. Web. doi:10.1016/j.actamat.2017.05.053.
Aydogan, E., Maloy, S. A., Anderoglu, O., Sun, C., Gigax, J. G., Shao, L., Garner, F. A., Anderson, I. E., & Lewandowski, J. J. Effect of tube processing methods on microstructure, mechanical properties and irradiation response of 14YWT nanostructured ferritic alloys. United States. doi:10.1016/j.actamat.2017.05.053.
Aydogan, E., Maloy, S. A., Anderoglu, O., Sun, C., Gigax, J. G., Shao, L., Garner, F. A., Anderson, I. E., and Lewandowski, J. J. Tue . "Effect of tube processing methods on microstructure, mechanical properties and irradiation response of 14YWT nanostructured ferritic alloys". United States. doi:10.1016/j.actamat.2017.05.053.
@article{osti_1407908,
title = {Effect of tube processing methods on microstructure, mechanical properties and irradiation response of 14YWT nanostructured ferritic alloys},
author = {Aydogan, E. and Maloy, S. A. and Anderoglu, O. and Sun, C. and Gigax, J. G. and Shao, L. and Garner, F. A. and Anderson, I. E. and Lewandowski, J. J.},
abstractNote = {In this research, innovative thermal spray deposition (Process I) and conventional hot extrusion processing (Process II) methods have been used to produce thin walled tubing (~0.5 mm wall thickness) out of 14YWT, a nanostructured ferritic alloy. The effects of processing methods on the microstructure, mechanical properties and irradiation response have been investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and, micro- and nano-hardness techniques. It has been found that these two processes have a significant effect on the microstructure and mechanical properties of the as-fabricated 14YWT tubes. Even though both processing methods yield the formation of various size Y-Ti-O particles, the conventional hot extrusion method results in a microstructure with smaller, homogenously distributed nano-oxides (NOs, Y-Ti-O particles < 5 nm) with higher density. Therefore, Process II tubes exhibit twice the hardness of Process I tubes. It has also been found that these two tremendously different initial microstructures strongly affect irradiation response in these tubes under extremely high dose ion irradiations up to 1100 peak dpa at 450 °C. The finer, denser and homogenously distributed NOs in the Process II tube result in a reduction in swelling by two orders of magnitude. On the other hand, inhomogeneity of the initial microstructure in the Process I tube leads to large variations in both swelling and irradiation induced hardening. Moreover, hardening mechanisms before and after irradiation were measured and compared with detailed calculations. In conclusion, this study clearly indicates the crucial effect of initial microstructure on radiation response of 14YWT alloys.},
doi = {10.1016/j.actamat.2017.05.053},
journal = {Acta Materialia},
number = C,
volume = 134,
place = {United States},
year = {Tue Jun 06 00:00:00 EDT 2017},
month = {Tue Jun 06 00:00:00 EDT 2017}
}

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  • In this research, innovative thermal spray deposition (Process I) and conventional hot extrusion processing (Process II) methods have been used to produce thin walled tubing (~0.5 mm wall thickness) out of 14YWT, a nanostructured ferritic alloy. The effects of processing methods on the microstructure, mechanical properties and irradiation response have been investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and, micro- and nano-hardness techniques. It has been found that these two processes have a significant effect on the microstructure and mechanical properties of the as-fabricated 14YWT tubes. Even though both processing methods yield the formation of variousmore » size Y-Ti-O particles, the conventional hot extrusion method results in a microstructure with smaller, homogenously distributed nano-oxides (NOs, Y-Ti-O particles < 5 nm) with higher density. Therefore, Process II tubes exhibit twice the hardness of Process I tubes. It has also been found that these two tremendously different initial microstructures strongly affect irradiation response in these tubes under extremely high dose ion irradiations up to 1100 peak dpa at 450 °C. The finer, denser and homogenously distributed NOs in the Process II tube result in a reduction in swelling by two orders of magnitude. On the other hand, inhomogeneity of the initial microstructure in the Process I tube leads to large variations in both swelling and irradiation induced hardening. Moreover, hardening mechanisms before and after irradiation were measured and compared with detailed calculations. In conclusion, this study clearly indicates the crucial effect of initial microstructure on radiation response of 14YWT alloys.« less
  • In this paper, texture and microstructure of tubes and plates fabricated from a nanostructured ferritic alloy (14YWT), produced either by spray forming followed by hydrostatic extrusion (Process I) or hot extrusion and cross-rolling a plate followed by hydrostatic tube extrusion (Process II) have been characterized in terms of their effects on texture and grain boundary character. Hydrostatic extrusion results in a combination of plane strain and shear deformations which generate low intensity α- and γ-fiber components of {001}<110> and {111}<110> together with a weak ζ-fiber component of {011}<211> and {011}<011>. In contrast, multi-step plane strain deformation by hot extrusion andmore » cross-rolling of the plate leads to a strong texture component of {001}<110> together with a weaker {111}<112> component. Although the total strains are similar, shear dominated deformation leads to much lower texture indexes compared to plane strain deformations. Further, the texture intensity decreases after hydrostatic extrusion of the alloy plate formed by plane strain deformation, due to a lower number of activated slip systems during shear dominated deformation. Finally and notably, hot extruded and cross-rolled plate subjected to plane strain deformation to ~50% engineering strain creates only a modest population of low angle grain boundaries, compared to the much larger population observed following the combination of plane strain and shear deformation of ~44% engineering strain resulting from subsequent hydrostatic extrusion.« less
  • Texture and microstructure of tubes and plates fabricated from a nanostructured ferritic alloy (14YWT), produced either by spray forming followed by hydrostatic extrusion (Process I) or hot extrusion and cross-rolling a plate followed by hydrostatic tube extrusion (Process II) have been characterized in terms of their effects on texture and grain boundary character. Hydrostatic extrusion results in a combination of plane strain and shear deformations which generate low intensity α- and γ-fiber components of {001}<110> and {111}<110> together with a weak ζ-fiber component of {011}<211> and {011}<011>. In contrast, multi-step plane strain deformation by hot extrusion and cross-rolling of themore » plate leads to a strong texture component of {001}<110> together with a weaker {111}<112> component. Although the total strains are similar, shear dominated deformation leads to much lower texture indexes compared to plane strain deformations. In addition, the texture intensity decreases after hydrostatic extrusion of the alloy plate formed by plane strain deformation, due to a lower number of activated slip systems during shear dominated deformation. Notably, hot extruded and cross-rolled plate subjected to plane strain deformation to ~50% engineering strain creates only a modest population of low angle grain boundaries, compared to the much larger population observed following the combination of plane strain and shear deformation of ~44% engineering strain resulting from subsequent hydrostatic extrusion.« less
  • Cited by 5
  • Nanostructured ferritic alloys (NFAs) have outstanding high temperature creep properties and extreme tolerance to radiation damage. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of -Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of -Fe with 50-100 m irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embeddedmore » precipitates with the Al5Y3O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These differences can be explained by the differences in the microstructure and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms retarding diffusion.« less