Low-cyclic fatigue behaviour of an Al–Cu–Mg–Ag alloy under T6 and T840 conditions

Abstract

The low-cyclic fatigue (LCF) behaviour of an AA2139 alloy belonging to the Al-Cu-Mg-Ag system was investigated under T6 and T840 conditions. The T840 treatment involves cold rolling with a 40% reduction prior to ageing, and this was effective in increasing the tensile strength of the alloy. Under cyclic loading at total strain amplitudes (ε ac ) of ±0.4 to ±1.0%, the mechanical behaviour is defined as the prevalence of elastic over plastic deformation processes under both the T6/T840 conditions. The initial weak hardening during one to two cycles of loading at ε ac > 0.55% and an insignificant softening upon following the cyclic loading to fracture was observed for the T6/T840 conditions. The LCF behaviour of the alloy under the T6/T840 conditions is described by the Basquin-Manson-Coffin relationship.

Edge interfaces of the Ω plates in a peak-aged Al-Cu-Mg-Ag alloy

“…Al-Cu-Mg-Ag alloys exhibit high specific strength, good fracture toughness and fatigue fracture in addition to superior creep resistance at elevated temperatures. This is attributed to the uniformly dispersed Ω-phase formed during aging as well as its thermal resistance to coarsening [1][2][3][4][5][6][7][8][9][10].…”

“…As the plate thickens during aging, the elastic properties of the plate would be expected to more closely approach those of the bulk [8] and elastic strain fields can be localized in the adjacent Al matrix. Analysis of the edge interfaces may shed light on strain field distributions around the {111} Al plates, knowing of which can help to understand mechanisms of {111} Al plate strengthening in aged aluminum alloys [10,[32][33][34]; preferential Ω-phase orientations observed in the stressaged Al-Cu-Mg-Ag alloys [27][28][29][30].…”

Influence of θ′ Phase Cutting on Precipitate Hardening of Al–Cu Alloy during Prolonged Plastic Deformation: Molecular Dynamics and Continuum Modeling

“…One of the possible reasons for this may be a decrease in the efficiency of accumulation of the Orowan loops around the inclusion after the cutting [15]. The authors of work [17] observed the softening of AA2139 alloy samples under cycle loading; this softening was explained as a consequence of the repeated cutting of Ω phases. Besides precipitate cutting, accumulation of microvoids is observed in the shear bands that can further initiate the fracture of the deformed sample [18].…”

Statistical Model for the Mechanical Properties of Al-Cu-Mg-Ag Alloys at High Temperatures

“…Many recent publications [1,7,8] have focused on investigating the evolution of microstructure and mechanical properties in these alloys.…”

“…Thus, the objective of many researches, recently, is to develop and design new aluminum alloys with precipitates that are stable at high temperatures. The use of Al-Cu-Mg-Ag aluminum alloys (AA2139 and AA2519) has increased substantially in aircraft and military applications due to their low density, exceptional toughness, and moderately high-temperature stability [1][2][3].…”