Characteristics of the Transition from Grain-Boundary Sliding to Solute Drag Creep in Superplastic AA5083

Abstract

Superplastic tensile ductility has been attained when specially-processed AA5083 materials are strained in tension at relatively high strain rates, in the range of the transition from grainboundary sliding (GBS) to solute drag creep (SDC) control of deformation. Quick plastic forming (QPF) technology involves deformation at such strain rates, and the relative contributions of GBS and SDC to the strain during deformation in this strain rate regime have been examined in this investigation. The additive, independent contributions of GBS and SDC to the elevated temperature deformation of fine-grained materials are reviewed. The transition from GBS to SDC in grain-refined AA5083 materials was evaluated by several methods, including the assessment of initial transients during straining and of transients during strain-rate change tests; the strain-rate dependence of the flow stress; the dependence of ductility on strain rate; flow localization behavior and fracture mode; cavitation growth; the evolution of microstructure and microtexture during deformation; and comparison with phenomenological models for the GBS-to-SDC transition.

Achieving microstructures prone to superplastic deformation in an Al–Zn–Mg–Cu alloy by equal channel angular pressing

“…Furthermore, as it will be seen below, a significant shift in the misorientation distribution toward random texture is obtained after deformation in the gauge length. This texture evolution is in contrast to microstructures that evolve during superplastic straining via a continuous recrystallization, where retention of prior deformation textures and gradual evolution of high-angle boundaries are observed during superplastic straining [37]. On the other hand, the grain size in the gauge region is slightly finer than in the grip region.…”

Friction Stir Processing (FSP) of Cast Metals: Microstructure – Property Relationships in NiAl Bronze and AA5083

“…Test results for a series of five tests on the FS'ed material are compared in Fig. 7 to tests of conventional AA5083 produced by direct-chill casting and hot and cold rolling to 1.4mm thickness, and continuously cast AA5083 after conventional hot and cold rolling to the same thickness [11][12][13][14]. FSP has resulted in a reduction in flow stress and increase in strain rate for the maximum value of the strain rate sensitivity coefficient,…”

Effect of Microstructure on Cavitation during Hot Deformation of a Fine-Grained Aluminum-Magnesium Alloy as Revealed through Three-Dimensional Characterization

“…It is known from previous investigations [5,6,29] that each deformation mechanism can be produced at 450°C simply by applying different strain rates. Thus, temperature was kept constant at 450°C and strain rates were chosen, based upon prior experimental data, [5,6,29] to be 3 9 10 À4 s À1 to produce deformation dominated by GBS creep and 3 9 10 À2 s À1 to produce deformation dominated by SD creep. Previous results for the evolution of cavity area fraction with strain under each of these test conditions, [6] shown in Figure 1, served as a guide in designing experiments for this investigation.…”