Mechanisms influencing the cryogenic fracture-toughness behavior of aluminum-lithium alloys
- Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley (United States)
Cryogenic strength-toughness relationships for advanced aluminum-lithium alloys 2090, 8090, 8091 and 2091 are examined as a function of microstructure, plate orientation and wrought-product form (plate vs. sheet), with specific emphasis on the underlying micro-mechanisms associated with crack advance. It is found that, with decrease in temperature from 298 K to 77 and 4 K, strength, tensile elongation and strain-hardening exponent are increased for all alloy chemistries, microstructures and product forms; however, the longitudinal (L-T, T-L) fracture toughness may increase or decrease depending upon the prevailing microscopic mechanism (microvoid coalescence vs transgranular shear) and macroscopic mode (plane strain vs plane stress) of fracture. In general, alloy microstructures that exhibit changes in either the fracture mechanism or mode at low temperatures show a decrease in L-T toughness. Conversely, when the fracture mechanism is unchanged between ambient and 4K, observed variations in toughness with temperature are a strong function of the degree of local stress-triaxiality that develops at the crack tip. 55 refs., 18 figs., 2 tabs.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 7267093
- Journal Information:
- Acta Metallurgica et Materialia; (United States), Vol. 38:11; ISSN 0956-7151
- Country of Publication:
- United States
- Language:
- English
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