Mechanisms of fatigue crack growth in Ti-48Al at ambient and elevated temperature

Journal Article · Sun Oct 01 04:00:00 EDT 1995 · Scripta Metallurgica et Materialia

DOI:https://doi.org/10.1016/0956-716X(95)00343-T· OSTI ID:237840

Soboyejo, W O; Mercer, C ^[1]; Aswath, P B ^[2]

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1. Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering
2. Univ. of Texas, Arlington, TX (United States)

Gamma-based titanium aluminides are of practical interest due to their potential to replace nickel- and cobalt-based alloys in aeroengines. The results of a study of crack-tip deformation on the mechanisms of fatigue crack growth in a model powder metallurgy (P/M) gamma-based titanium aluminide intermetallic (Ti-48Al) are presented in this paper. Note that compositions are quoted in atomic % unless stated otherwise. Crack-tip deformation is shown to occur by a combination of deformation-induced twinning and conventional slip at room temperature, and conventional reversed plasticity/slip only at elevated temperature (700 C). Differences between crack-tip deformation mechanisms at room- and elevated-temperature are explained by crack-tip transmission electron microscopy (TEM) analysis. The potential effects of twin toughening are also quantified using optical interference measurements of twin process zones and micromechanical models. The implications of the different crack-tip deformation mechanisms for cyclic irreversibility are discussed for crack growth at room- and elevated-temperature. The results suggest that slower fatigue crack growth rates at elevated-temperature are due to differences in crack-tip deformation and closure mechanisms.

• OSTI ID: 237840
• Journal Information: Scripta Metallurgica et Materialia, Journal Name: Scripta Metallurgica et Materialia Journal Issue: 7 Vol. 33; ISSN SCRMEX; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
36 MATERIALS SCIENCE
AIRCRAFT
ALUMINIUM ALLOYS
CRACKS
DEFORMATION
ENGINES
EXTRUSION
FATIGUE
INTERMETALLIC COMPOUNDS
OPTICAL EQUIPMENT
PLASTICITY
POWDERS
SLIP
TEMPERATURE DEPENDENCE
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY
TWINNING