Temperature-dependent void-sheet fracture in Al-Cu-Mg-Ag-Zr

Journal Article · Mon Jun 01 04:00:00 EDT 1998 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-998-0084-3· OSTI ID:634642

Haynes, M J ^[1]; Gangloff, R P ^[2]

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1. Texas Instruments, Inc., Attleboro, MA (United States)
2. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering

Temperature-dependent initiation fracture toughness and stable crack growth resistance are important attributes of next-generation aluminum alloys for airframe applications such as the high speed civil transport. Previous research showed that tensile fracture strain increases as temperature increases for AA2519 with Mg and Ag additions, because the void-sheet coalescence stage of microvoid fracture is retarded. The present work characterizes intravoid-strain localization (ISL) between primary voids at large constituents and secondary-void nucleation at small dispersoids, two mechanisms that may govern the temperature dependence of void sheeting. Most dispersoids nucleate secondary voids in an ISL band at 25 C, promoting further localization, while dispersoid-void nucleation at 150 C is greatly reduced. Increased strain-rate hardening with increasing temperature does not cause this behavior. Rather, a stress relaxation model predicts that flow stress and strain hardening decrease with increasing temperature or decreasing strain rate due to a transition from dislocation accumulation to diffusional relaxation around dispersoids. This transition to softening causes a sharp increase in the model-predicted applied plastic strain necessary for dispersoid/matrix interface decohesion. This reduced secondary-void nucleation and reduced ISL at elevated temperature explain retarded void sheeting and increased fracture strain.

• Sponsoring Organization: USDOE
• OSTI ID: 634642
• 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: 6 Vol. 29; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
36 MATERIALS SCIENCE
AIRCRAFT
ALUMINIUM BASE ALLOYS
FLOW STRESS
FRACTURE PROPERTIES
STRAIN HARDENING
STRAINS
TEMPERATURE DEPENDENCE
VOIDS