The effect of cold rotary swaging (RS) and subsequent aging on the structure, electrical conductivity, mechanical characteristics and fracture toughness of the Cu-0.77%Cr-0.86%Hf alloy was studied. RS leads to the formation of a microstructure elongated along the direction of deformation with grains width of 8.0 ± 0.2 μm. An ultrafine-grained structure with shear bands of 370 ± 10 nm in width and subgrains of 500 ± 13 nm in size is formed inside these elongated grains. The refinement of the microstructure after RS leads to an increase in ultimate tensile strength (UTS) from 300 ± 5 to 505 ± 12 MPa and a decrease in ductility from 54.0 ± 2.4 to 12.9 ± 0.3%. A subsequent aging of the alloy leads to the precipitation of fine particles of Cr and Cu 5 Hf phases. The precipitation of these particles leads to an additional increase in UTS of RS-treated alloy up to 558 ± 11 MPa and ductility up to 15.4 ± 2.4%. In this case, the decomposition of the supersaturated solid solution, which accompanies the particles precipitation, leads to an increase in the electrical conductivity of the deformed alloy up to 77.7 ± 1.6%IACS. The combination of RS and subsequent aging at a temperature of 450 °C for 4 h leads to an increase in the fatigue limit from 220 to 393 MPa. In addition, this treatment allows to increase the fracture toughness coefficient by 6 times.

The effect of cold rotary swaging (RS) and subsequent aging on the structure, electrical conductivity, mechanical characteristics and fracture toughness of the Cu-0.77

Magnesium alloy Mg-1.0%Zn-0.3%Ca was processed by equal channel angular pressing (ECAP) with the aim to refine its microstructure. ECAP was found to reduce the average grain size from 106.0 +/- 2.05 mu m in the initial state to 4.0 +/- 0.19 mu m and 8.0 +/- 0.18 mu m in the transverse and longitudinal sections, respectively. This resulted in a slight strengthening (the yield strength and the ultimate tensile strength rose from 92 and 194 MPa in the initial stat to 106 and 215 MPa after processing, respectively). The main advantage of ECAP is the concurrent increase of tensile elongation from 12.8% to 23.9%. The absence of pronounced strengthening and a significant increase in ductility are associated with the formation of an inclined basal texture, along with activation of prismatic slip during ECAP. It was also shown that ECAP leads to an increase in the fatigue limit of the alloy from 100 MPa to 110 MPa and does not impair its resistance to chemical corrosion. (C) 2018 Elsevier B.V. All rights reserved.

Microstructure (including its uniformity), texture, and mechanical properties of Mg-Al-Zn-Mn alloy billets after radial-shear rolling (RSR) were investigated. RSR with the temperature in the interval 420 -140 degrees C and true strain up to 2.63 was shown to lead to grain refinement down to 1.5-3.5 mu m (as determined by optical microscopy). The microstructure was found to be reasonably uniform over the transversal cross-sections of the billets. The transmission electron microscopy analysis also revealed submicron sized grains and the formation of two types of particles: Mg17Al12 particles 300-500 nm in size and MgAl nanoparticles of different shapes 20-40 nm in size. Increments in strain and step-wise decrease in deformation temperature with the number of RSR passes was found to lead to a transformation of the initial basal texture to the prismatic texture. The RSR of the Mg-Al-Zn-Mn magnesium alloy was demonstrated to result in significant strength and good ductility owing to a fortunate interplay between fine grain structure and favorable texture promoting activity of non-basal slip systems. (C) 2018 Elsevier B.V. All rights reserved.