skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Loading rate and test temperature effects on fracture of in situ niobium silicide-niobium composites

Abstract

Arc cast, extruded, and heat-treated in situ composites of niobium silicide (Nb{sub 5}Si{sub 3}) intermetallic with niobium phases (primary--Nb{sub p} and secondary--Nb{sub s}) exhibited high fracture resistance in comparison to monolithic Nb{sub 5}Si{sub 3}. In toughness tests conducted at 298 K and slow applied loading rates, the fracture process proceeded by the microcracking of the Nb{sub 5}Si{sub 3} and plastic deformation of the Nb{sub p} and Nb{sub s} phases, producing resistance-curve behavior and toughnesses of 28 MPa{radical}m with damage zone lengths less than 500 {micro}m. The effects of changes in the Nb{sub p} yield strength and fracture behavior on the measured toughnesses were investigated by varying the loading rates during fracture tests at both 77 and 298 K. Quantitative fractography was utilized to completely characterize each fracture surface created at 298 K in order to determine the type of fracture mode (i.e., dimpled, cleavage) exhibited by the Nb{sub p}. Specimens tested at either higher loading rates or lower test temperatures consistently exhibited a greater amount of cleavage fracture in the Nb{sub p}, while the Nb{sub s} always remained ductile. However, the fracture toughness values determined from experiments spanning six orders of magnitude in loading rate at 298 and 77 Kmore » exhibited little variation, even under conditions when the majority of Nb{sub p} phases failed by cleavage at 77 K. The changes in fracture mode with increasing loading rate and/or decreasing test temperature and their effects on fracture toughness are rationalized by comparison to existing theoretical models.« less

Authors:
;  [1]
  1. Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
417883
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 27; Journal Issue: 10; Other Information: PBD: Oct 1996
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COMPOSITE MATERIALS; FRACTURE PROPERTIES; NIOBIUM SILICIDES; NIOBIUM; INTERMETALLIC COMPOUNDS; SAMPLE PREPARATION; CASTING; EXTRUSION; HEAT TREATMENTS; CRACKS; PLASTICITY; YIELD STRENGTH; FRACTOGRAPHY; CLEAVAGE; STRESSES; BRITTLENESS; DUCTILITY; TEMPERATURE DEPENDENCE

Citation Formats

Rigney, J D, and Lewandowski, J J. Loading rate and test temperature effects on fracture of in situ niobium silicide-niobium composites. United States: N. p., 1996. Web. doi:10.1007/BF02663879.
Rigney, J D, & Lewandowski, J J. Loading rate and test temperature effects on fracture of in situ niobium silicide-niobium composites. United States. https://doi.org/10.1007/BF02663879
Rigney, J D, and Lewandowski, J J. Tue . "Loading rate and test temperature effects on fracture of in situ niobium silicide-niobium composites". United States. https://doi.org/10.1007/BF02663879.
@article{osti_417883,
title = {Loading rate and test temperature effects on fracture of in situ niobium silicide-niobium composites},
author = {Rigney, J D and Lewandowski, J J},
abstractNote = {Arc cast, extruded, and heat-treated in situ composites of niobium silicide (Nb{sub 5}Si{sub 3}) intermetallic with niobium phases (primary--Nb{sub p} and secondary--Nb{sub s}) exhibited high fracture resistance in comparison to monolithic Nb{sub 5}Si{sub 3}. In toughness tests conducted at 298 K and slow applied loading rates, the fracture process proceeded by the microcracking of the Nb{sub 5}Si{sub 3} and plastic deformation of the Nb{sub p} and Nb{sub s} phases, producing resistance-curve behavior and toughnesses of 28 MPa{radical}m with damage zone lengths less than 500 {micro}m. The effects of changes in the Nb{sub p} yield strength and fracture behavior on the measured toughnesses were investigated by varying the loading rates during fracture tests at both 77 and 298 K. Quantitative fractography was utilized to completely characterize each fracture surface created at 298 K in order to determine the type of fracture mode (i.e., dimpled, cleavage) exhibited by the Nb{sub p}. Specimens tested at either higher loading rates or lower test temperatures consistently exhibited a greater amount of cleavage fracture in the Nb{sub p}, while the Nb{sub s} always remained ductile. However, the fracture toughness values determined from experiments spanning six orders of magnitude in loading rate at 298 and 77 K exhibited little variation, even under conditions when the majority of Nb{sub p} phases failed by cleavage at 77 K. The changes in fracture mode with increasing loading rate and/or decreasing test temperature and their effects on fracture toughness are rationalized by comparison to existing theoretical models.},
doi = {10.1007/BF02663879},
url = {https://www.osti.gov/biblio/417883}, journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
number = 10,
volume = 27,
place = {United States},
year = {1996},
month = {10}
}