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Title: Microstructures of the Hot-Deformed Ti-Al-Nb-W-B Alloys

Abstract

No abstract prepared.

Authors:
 [1];  [2];  [1]
  1. ORNL
  2. University of Tennessee, Knoxville (UTK)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
FE USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
933061
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 21st Annual Conference on Fossil Enery Materials, Knoxville, TN, USA, 20070430, 20070502
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM BORIDES; NIOBIUM BORIDES; TITANIUM BORIDES; TUNGSTEN BORIDES; MICROSTRUCTURE

Citation Formats

Huang, Lan, Liaw, Peter K, and Liu, Chain T. Microstructures of the Hot-Deformed Ti-Al-Nb-W-B Alloys. United States: N. p., 2007. Web.
Huang, Lan, Liaw, Peter K, & Liu, Chain T. Microstructures of the Hot-Deformed Ti-Al-Nb-W-B Alloys. United States.
Huang, Lan, Liaw, Peter K, and Liu, Chain T. Mon . "Microstructures of the Hot-Deformed Ti-Al-Nb-W-B Alloys". United States. doi:.
@article{osti_933061,
title = {Microstructures of the Hot-Deformed Ti-Al-Nb-W-B Alloys},
author = {Huang, Lan and Liaw, Peter K and Liu, Chain T},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • The as-cast structure of Nb-Al-Ti alloys containing 15 at.% Al and 10, 25 and 40 at.% Ti has been characterized using transmission electron microscopy. The 10Ti alloy contained some {delta} (based on Nb{sub 3}Al) phase heterogeneously distributed on the matrix grain boundaries. The matrix had the ordered B2 structure. The 25Ti and 40Ti alloys had the single phase B2 structure. The electron diffraction patterns of the B2 structure showed diffuse intensities and streaking between fundamental spots. The domain structure was very fine and difficult to resolve. The structure of the as-cast alloys after compression testing to approximately 5% strain atmore » 25, 600 and 900 C was also characterized. The B2 structure was retained in the tested specimens. No additional phases were identified, but the diffuse intensities and streaking were apparent in the electron diffraction patterns. In the specimens tested at elevated temperatures, the domain structure was easily resolved, with irregular boundaries. The increase in the domain size is due to aging during testing. The dislocation structure in the specimens tested at 25 C and 600 C consisted of narrow intersecting bands with dislocation tangle between them. The bands were less defined for specimens tested at 900 C. It was found that the compressive strength increased with increasing Nb content, which is probably due to solid solution strengthening, and not to fine precipitates, such as the {omega} and o phases, which may have formed.« less
  • Fe-16Cr-17Ni ternary alloy and those with addition of 0.024P, 0.1P and 0.1P + 0.25Ti were irradiated with fast neutrons in FFTF/MOTA at 793 K and 874 K to 33 dpa and 60 dpa. For the purpose of investigating helium production effect, two levels of {sup 10}B were doped for each alloy. The microstructures and their relation with tensile properties were examined. The yield stress change was correlated with the density of phosphide precipitates.
  • In Part 1 of this paper possible transformation paths that involve no long range diffusion and their corresponding microstructural details were predicted for Ti-Al-Nb alloys cooled from the high temperature b.c.c./B2 phase field into close-packed orthorhombic or hexagonal phase fields. In the present paper experimental TEM results show that two of the predicted transformation paths are indeed followed for different alloy compositions. For Ti-25Al-12.5Nb (at.%), the path includes the formation of intermediate hexagonal phases, A3 and D0[sub 19], and subsequent formation of a metastable domain structure of the low-temperature O phase. For alloys close to Ti-25Al-25Nb (at.%), the path involvesmore » an intermediate B19 structure and subsequent formation of a translational domain structure of the O phase. The path selection depends on whether B2 order forms in the high temperature cubic phase prior to transformation to the close-packed structure. The paper also analyzes the formation of a two-phase modulated microstructure during long term annealing 700 C. The thermodynamics underlying the path selection and the two-phase formation are also discussed.« less
  • Three exceptionally high-toughness Fe-12% Ni alloys designed for cryogenic service were welded using the GTA welding process. Evaluation of weldability included equivalent energy K/sub Icd/ fracture toughness tests, transverse-weld tensile tests at -196 and 25 C (-321 and 77 F) and weld crack sensitivity tests. The Fe-12% Ni-0.25% Ti alloy proved extremely weldable for cryogenic applications, having weld and heat-affected zone properties comparable with those of the wrought base alloy. The Fe-12% Ni-0.5% Al had good weld properties only after the weld joint was heat treated. The Fe-12% Ni-0.25% Nb alloy was not considered weldable for cryogenic use because ofmore » its poor weld joint properties at -196 C and its susceptibility to hot cracking.« less
  • Development of {alpha}{sub 2}-Ti{sub 3}Al based dual phase alloys have shown some promising potentials in property improvement by introducing Ti{sub 5}Si{sub 3} silicide phase into the matrix via Si alloying. However, the presence of coarse network of Ti{sub 5}Si{sub 3} phase formed by eutectic reaction in the as-cast state also embrittles the alloy. Both hot rolling and powder metallurgy are considered to be the possible ways to refine the Ti{sub 5}Si{sub 3} phase in the matrix. Two Ti-Al-Si-Nb alloys whose Si contents are 2 and 5 at.% respectively were arc melted into ingots and then hot rolled to sheets inmore » this investigation. Optical metallographic examination correlates the microstructures of the as-cast and as-rolled alloys with the different rolling amounts, showing that the coarse silicide network is broken into small particles after hot rolling. Mechanical property testing from room temperature to 800 C indicates that the strength and plastic elongation of the hot-rolled alloys are much higher than those of the as-cast ones. The data obtained in this investigation are comparable with those obtained in the P/M processed specimens. Fracture surfaces of the alloys are also examined.« less