Ivan Zuiko

Effect of Cold Plastic Deformation Prior to Ageing on Creep Resistance of an Al-Cu-Mg-Ag Alloy

Effect of thermomechanical processing on creep resistance at 150°C of an Al-5.6Cu-0.72Mg-0.5Ag-0.32Mn-0.17Sc-0.12Zr (wt. %) alloy was examined. It was shown that increasing strain prior to artificial aging provides achieving high strength. However, a degradation of the creep resistance, i.e., significant decrease in the rupture time and increase in the minimal creep rate, took place, concurrently. The effect of cold rolling on the strength and creep resistance is discussed in relation with the strain effect on the dispersion of secondary phases. The increase in strength and degradation of creep properties of the alloy subjected to cold working before ageing result from superposition of two competitive processes. First, an increase in the lattice dislocation density facilitates the precipitation of Ω-phase plates with high aspect ratio, leading to increase in the static strength at room temperature. Second, acceleration of the diffusion processes results in coarsening of strengthening phase in grain/subgrain interiors and precipitation of Ω-phase on deformation-induced boundaries during creep that deteriorates creep resistance.

Effect of Cold Plastic Deformation on Mechanical Properties of Aluminum Alloy 2519 After Ageing

Effect of cold plastic deformation prior to ageing at 180°C on a microstructure and mechanical properties at room temperature for an AA2519 alloy was examined subjected to solution treatment and water quenching initially. It was found that cold rolling with a reduction of 15% or equal-channel angular pressing (ECAP) up to a true strain of ~1 leads to acceleration of age-hardening response of this alloy. Peak hardness values of 127, 175 and 169 HV0.2 were achieved by ageing following quenching, cold rolling and ECAP, respectively. The highest values of yield stress (YS) of 475 MPa and ultimate tensile strength (UTS) of 520 MPa, were attained after ECAP followed by ageing. The effect of cold plastic deformation prior to ageing on the precipitation behavior and its relation with mechanical properties of the AA2519 is discussed.

Superplasticity of an AA2519 Aluminum Alloy

A commercial AA2519 alloy with a chemical composition of Al-5.64Cu-0.33Mn-0.23Mg-0.15Zr (in wt. %) was subjected to two-step thermomechanical processing (TMP) providing the formation of fully recrystallized structure with an average grain size of ~7 mm in 3 mm thin sheets. Superplastic tensile tests were performed in the temperature interval 450-535°C and initial strain rates ranging from ~2.8 x 10-4 to ~6.0 x 10-1 s-1. The highest elongation-to-failure of ~750% appears at a temperature of ~525°C and an initial strain rate of ~1.4 × 10-4 s-1 with the corresponding strain rate sensitivity coefficient of ~0.46.

Effect of Plastic Deformation on a Dispersion of Omega-Phase and Mechanical Properties of an Al-Cu-Mg-Ag Alloy

Effect of cold rolling prior to ageing on a dispersion of secondary phases and mechanical properties at room temperature for an Al-5.6Cu-0.72Mg-0.5Ag-0.32Mn-0.17Sc-0.12Zr (wt. %) alloy, which was solution treated and water quenched initially, was examined. It was shown that cold working leads to significant increase in density of lattice dislocations that induces the formation discrete agglomerates of the θ′-phase on the {100} planes. Strain of 7% provided increased aspect ratio (length to thickness) of plates that leads to moderate increase of strength. Imposing of higher strains leads to increased lattice dislocation density and the formation of deformation-induced boundaries. Precipitation of the coarse particles of secondary phases on these boundaries takes place. The high yield stress (YS) of 535 MPa and ultimate tensile strength (UTS) of 570 MPa, were attained after cold rolling with a reduction of 80% followed by ageing at 190°C for 2 h. The effect of plastic deformation prior to ageing on the precipitation behavior and strengthening of Al-Cu-Mg-Ag alloy is discussed.