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Title: High-temperature fracture and fatigue-crack growth behavior of an XD gamma-based titanium aluminide intermetallic alloy

Abstract

A study has been made of the effect of temperature (between 25 C and 800 C) on fracture toughness and fatigue-crack propagation behavior in an XD-processed, {gamma}-based titanium aluminide intermetallic alloy, reinforced with a fine dispersion of {approximately}1 vol pct TiB{sub 2} particles. It was found that, whereas crack-initiation toughness increased with increasing temperature, the crack-growth toughness on the resistance curve was highest just below the ductile-to-brittle transition temperature (DBTT) at 600 C; indeed, above the DBTT, at 800 C, no rising resistance curve was seen. Such behavior is attributed to the ease of microcrack nucleation above and below the DBTT, which, in turn, governs the extent of uncracked ligament bridging in the crack wake as the primary toughening mechanism. The corresponding fatigue-crack growth behavior was also found to vary inconsistently with temperature. The fastest crack growth rates (and lowest fatigue thresholds) were seen at 600 C, while the slowest crack growth rates (and highest thresholds) were seen at 800 C; the behavior at 25 C was intermediate. Previous explanations for this anomalous temperature effect in {gamma}-TiAl alloys have focused on the existence of some unspecified environmental embrittlement at intermediate temperatures or on the development of excessive crack closure atmore » 800 C; no evidence supporting these explanations could be found. The effect is now explained in terms of the mutual competition of two processes, namely, the intrinsic microstructural damage/crack-advance mechanism, which promotes crack growth, and the propensity for crack-tip blunting, which impedes crack growth, both of which are markedly enhanced by increasing temperature.« less

Authors:
; ;
Publication Date:
Research Org.:
Univ. of California, Berkeley, CA (US)
OSTI Identifier:
20075683
Alternate Identifier(s):
OSTI ID: 20075683
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 31; Journal Issue: 5; Other Information: PBD: May 2000; Journal ID: ISSN 1073-5623
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; FRACTURE PROPERTIES; FATIGUE; TITANIUM ALLOYS; ALUMINIUM ALLOYS; BORON ADDITIONS; INTERMETALLIC COMPOUNDS; TEMPERATURE DEPENDENCE; CRACK PROPAGATION

Citation Formats

McKelvey, A.L., Venkateswara Rao, K.T., and Ritchie, R.O. High-temperature fracture and fatigue-crack growth behavior of an XD gamma-based titanium aluminide intermetallic alloy. United States: N. p., 2000. Web. doi:10.1007/s11661-000-0259-z.
McKelvey, A.L., Venkateswara Rao, K.T., & Ritchie, R.O. High-temperature fracture and fatigue-crack growth behavior of an XD gamma-based titanium aluminide intermetallic alloy. United States. doi:10.1007/s11661-000-0259-z.
McKelvey, A.L., Venkateswara Rao, K.T., and Ritchie, R.O. Mon . "High-temperature fracture and fatigue-crack growth behavior of an XD gamma-based titanium aluminide intermetallic alloy". United States. doi:10.1007/s11661-000-0259-z.
@article{osti_20075683,
title = {High-temperature fracture and fatigue-crack growth behavior of an XD gamma-based titanium aluminide intermetallic alloy},
author = {McKelvey, A.L. and Venkateswara Rao, K.T. and Ritchie, R.O.},
abstractNote = {A study has been made of the effect of temperature (between 25 C and 800 C) on fracture toughness and fatigue-crack propagation behavior in an XD-processed, {gamma}-based titanium aluminide intermetallic alloy, reinforced with a fine dispersion of {approximately}1 vol pct TiB{sub 2} particles. It was found that, whereas crack-initiation toughness increased with increasing temperature, the crack-growth toughness on the resistance curve was highest just below the ductile-to-brittle transition temperature (DBTT) at 600 C; indeed, above the DBTT, at 800 C, no rising resistance curve was seen. Such behavior is attributed to the ease of microcrack nucleation above and below the DBTT, which, in turn, governs the extent of uncracked ligament bridging in the crack wake as the primary toughening mechanism. The corresponding fatigue-crack growth behavior was also found to vary inconsistently with temperature. The fastest crack growth rates (and lowest fatigue thresholds) were seen at 600 C, while the slowest crack growth rates (and highest thresholds) were seen at 800 C; the behavior at 25 C was intermediate. Previous explanations for this anomalous temperature effect in {gamma}-TiAl alloys have focused on the existence of some unspecified environmental embrittlement at intermediate temperatures or on the development of excessive crack closure at 800 C; no evidence supporting these explanations could be found. The effect is now explained in terms of the mutual competition of two processes, namely, the intrinsic microstructural damage/crack-advance mechanism, which promotes crack growth, and the propensity for crack-tip blunting, which impedes crack growth, both of which are markedly enhanced by increasing temperature.},
doi = {10.1007/s11661-000-0259-z},
journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
issn = {1073-5623},
number = 5,
volume = 31,
place = {United States},
year = {2000},
month = {5}
}