Relationship between fracture toughness and crack extension resistance curves (R curves) for Ti-6Al-4V alloys

Journal Article · Sun Mar 01 04:00:00 EST 1998 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-998-0269-9· OSTI ID:616434

Horiya, Takao ^[1]; Kishi, Teruo ^[2]

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1. Nippon Steel Corp., Chiba (Japan)
2. Univ. of Tokyo (Japan). Research Center for Advanced Science and Technology

The effects of microstructure, impurity content, and testing temperature on the fracture toughness (as measured by the crack tip opening displacement (CTOD)) and microcrack extension resistance curves (R curves) of Ti-6Al-4V alloys were examined. At 0 C, microstructure is the most influential factor in the toughness-strength relationship. Acicular microstructure specimens have a higher CTOD than specimens with equiaxed microstructures, regardless of strength (0.2 pct proof stress) and impurity content. At {minus}196 C, impurity content becomes a controlling factor in the toughness-strength relationship. Extra-low impurity (ELI) specimens, which have a lower impurity content, show a higher CTOD, irrespective of microstructure. Microcracks extended from the notch tip before the maximum load was reached during testing were investigated, and crack initiation ({delta}{sub i}) and extension-resistance properties were evaluated by obtaining exact R curves of the microcracks. At 0 C, specimens with different microstructures and different impurity contents have almost the same {delta}{sub i}, but acicular-microstructure specimens with a higher CTOD at a given strength show a greater crack extension resistance. At {minus}196 C, ELI specimens, which have a higher CTOD, show a larger crack extension resistance. It is concluded that the crack extension-resistance property of the microcracks extended from the notch tip before the maximum load is a controlling factor for the fracture toughness of Ti-6Al-4V alloys.

• Sponsoring Organization: USDOE
• OSTI ID: 616434
• 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: 3 Vol. 29; ISSN MMTAEB; ISSN 1073-5623
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CRACK PROPAGATION
FRACTURE PROPERTIES
IMPURITIES
MICROSTRUCTURE
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
TITANIUM BASE ALLOYS
VANADIUM ALLOYS