Precipitate/matrix incompatibilities related to the {111}Al Ω plates in an Al-Cu-Mg-Ag alloy

The atomic structure of Ω plates forming on {111}Al planes in an Al-Cu-Mg-Ag alloy has been investigated by Z-contrast atomic-resolution scanning transmission electron microscopy imaging and ab initio density functional theory calculations. Ω plates with different thicknesses have been studied in two peak-aged conditions: 150 °C for 24 h and 190 °C for 1.5 h. Volumetric and structural incompatibilities as unrelaxed misfit strains and shear components, respectively, between the Ω plates involving orthorhombic θ-phase fragments and Al matrix were found to be in the plates with thicknesses from 0 to 2.5 cθ (a normal direction to {111}Al). Two types of shear components: [−101]Al // [0−10]θ (τI) and [1−21]Al // [100]θ (τII) related to precipitate/matrix structural incompatibilities have been predicted by calculations. The shear components τI and τII have been found to be energetically favorable in the plates with different thicknesses. Comparing τI and τII absolute values in supercells involving the plates with different thicknesses, 2 cθ thick plates have a shear component close to zero. All the plates analyzed have precipitate/matrix volumetric incompatibilities with Al matrix as misfit strains along [111]Al // [001]θ, which distribute non-uniformly across the plate thickness. Large misfit strains concentrate at the broad plate interfaces, i.e. in Ag2Cu and Cui layers, and cause a prohibitively high barrier to thickening of the Ω precipitates.acceptedVersio

Microstructural Evolution in the 2219 Aluminum Alloy During Severe Plastic Deformation

Numerous investigations have demonstrated that intense plastic deformation is an attractive procedure for producing an ultrafine grain size in metallic materials. Torsional deformation under high pressure and equal-channel angular extrusion are two techniques that can produce microstructures with grain sizes in the submicrometer and nanometer range. Materials with these microstructures have many attractive properties. The microstructures formed by these two processing techniques are essentially the same and thus the processes occurring during deformation should be the same. Most previous studies have examined the final microstructures produced as a result of severe plastic deformation and the resulting properties. Only a limited number of studies have examined the evolution of microstructure. As a result, some important aspects of ultra-fine grain formation during severe plastic deformation remain unknown. There is also limited data on the influence of the initial state of the material on the microstructural evolution and mechanisms of ultra-fine grain formation. This limited knowledge base makes optimization of processing routes difficult and retards commercial application of these techniques. The objective of the present work is to examine the microstructure evolution during severe plastic deformation of a 2219 aluminum alloy. Specific attention is given to the mechanism of ultrafine grain formation as a result of severe plastic deformation

Structural changes in steel 10Kh9K3V1M1FBR due to creep

The evolution of microstructure in steel 10Kh9K3V1M1FBR during creep and in aging at 600-650°C is studied. The results are compared with data for steel P91. The role of cobalt in growth in the long-term strength is consideredyesBelgorod State Universit

Structural changes in steel 10Kh9K3V1M1FBR due to creep

yesThe evolution of microstructure in steel 10Kh9K3V1M1FBR during creep and in aging at 600-650°C is studied. The results are compared with data for steel P91. The role of cobalt in growth in the long-term strength is consideredBelgorod State Universit

Microstructural development during hot working of Mg-3AI-1Zn

he microstructural evolution is examined during the hot compression of magnesium alloy AZ31 for both wrought and as-cast initial microstructures. The influences of strain, temperature, and strain rate on the dynamically recrystallized microstructures are assessed. Both the percentage dynamic recrysallization (DRX) and the dynamically recrystallized grain size were found to be sensitive to the initial microstructure and the applied deformation conditions. Lower Z conditions (lower strain rates and higher temperatures) yield larger dynamically recrystallized grain sizes and increased percentages of DRX, as expected. The rate with which the percentage DRX increases for the as-cast material is considerably lower than for the wrought material. Also, in the as-cast samples, the percentage DRX does not continue to increase toward complete DRX with decreasing Z. These observations may be attributed to the deformation becoming localized in the DRX fraction of the material. Also, the dynamically recrystallized grain size is generally larger in as-cast material than in wrought material, which may be attributed to DRX related to twins and the inhomogeneity of deformation. Orientation maps of the as-cast material (from electron backscattering diffraction (EBSD) data) reveal evidence of discontinuous DRX (DDRX) and DRX related to twins as predominant mechanisms, with some manifestation of continuous DRX (CDRX) and particle-stimulated nucleation (PSN).<br /