The fatigue and fracture resistance of a Nb-Cr-Ti-Al alloy

Journal Article · Sun Aug 01 04:00:00 EDT 1999 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-999-0011-2· OSTI ID:691373

Davidson, D L; Chan, K S ^[1]

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1. Southwest Research Inst., San Antonio, TX (United States)

The microstructure, fatigue, and fracture behaviors of a cast and heat-treated Nb-Cr-Ti-Al alloy were investigated. The microstructure of the cast alloy was manipulated by annealing at a temperature ranging from 500 C to 1500 C for 1 to 24 hours. The heat treatment produced Cr{sub 2}Nb precipitates along grain boundaries in all cases except in the 500 C heat-treated material. Fracture toughness tests indicated low fracture resistance in both the as-cast and heat-treated materials. Fatigue crack growth tests performed on the 500 C heat-treated material also indicated a low fatigue crack growth resistance. Direct observations of the near-tip region revealed a cleavage-dominated fracture process, in accordance with fractographic evidence. The fracture behavior of the Nb-Cr-Ti-Al alloy was compared to that of other Nb-Cr-Ti alloys. In addition, theoretical calculations of both the unstable stacking energy (USE) and Peierls-Niabarro (P-N) barrier energy are used to elucidate the role of Al additions in cleavage fracture of the Nb-Cr-Ti-Al alloy. The results indicate that an Al alloying addition increases the USE, which, in turn, prevents the emission of dislocations, promotes the nucleation and propagation of cleavage cracks from the crack up, and leads to a reduction in the fracture toughness.

• Sponsoring Organization: USDOE
• OSTI ID: 691373
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 8 Vol. 30; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
FATIGUE
FRACTURE PROPERTIES
HEAT TREATMENTS
MICROSTRUCTURE
NIOBIUM ALLOYS
PRECIPITATION
TEMPERATURE DEPENDENCE
TITANIUM ALLOYS