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Investigation of fatique crack growth rate of Al 5484 ultrafine grained alloy after ECAP process
Author(s) -
Brynk Tomasz,
Rasiński Marcin,
Pakieła Zbigniew,
Olejnik Lech,
Kurzydłowski Krzysztof J.
Publication year - 2010
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200983368
Subject(s) - materials science , pressing , alloy , grain size , ultimate tensile strength , severe plastic deformation , metallurgy , deformation (meteorology) , paris' law , fracture mechanics , composite material , crack closure
Abstract During the last decade equal‐channel angular pressing (ECAP) has emerged as a widely used fabrication route of ultrafine‐grained (UFG) metals and alloys. Enhanced mechanical properties of UFG materials produced by severe plastic deformation, with a grain size smaller than 1 µm, have been reported in a large number of publications. However, the higher strength does not imply higher resistance to fatigue both high‐ and low‐cyclic. In fact, due to reduced plasticity, higher fatigue crack propagation rates are reported for UFG materials, particularly in low‐amplitude range. The aim of this work was to investigate fatigue crack propagation in samples of Al 5483 alloy subjected to ECAP treatment. Because of small dimensions of the coupons processed by ECAP, non‐standard, mini‐samples were used in a crack propagation tests. Two test procedures were used to estimate stress intensity factor ( K ). The first was based on optical measurements of crack length from images recorded during the test. The second method was based on digital image correlation (DIC), which was used to determine K value directly from displacement field near the crack tip. Comparison of these two methods is made and the relationship between the intensity of ECAP process (measured in terms of the number of ECAP passes) and fatigue crack propagation rates proposed. In addition to fatigue resistance, the results of tensile tests carried out with mini‐samples are presented. Applicability of such samples in the investigations of the mechanical properties of UFG materials is discussed.