Plastic Flow Properties and Microstructural Evolution in an Ultrafine-Grained Al-Mg-Si Alloy at Elevated Temperatures

Abstract

An AA6082 alloy was subjected to eight passes of equal channel angular pressing at 100°C, resulting in an ultrafine grain size of 0.2 to 0.4 lm. The tensile deformation behavior of the material was studied over the temperature range of 100°C to 350°C and strain rate range of 10 À4 to 10 À1 s À1 . The evolution of microstructure under tensile deformation was investigated by analyzing both the deformation relief on the specimen surface and the dislocation structure. While extensive microshear banding was found at the lower temperatures of 100°C to 150°C, deformation at higher temperatures was characterized by cooperative grain boundary sliding and the development of a bimodal microstructure. Dislocation glide was identified as the main deformation mechanism within coarse grains, whereas no dislocation activity was apparent in the ultrafine grains.

Enhanced Mechanical Properties and Electrical Conductivity in Ultrafine-Grained Al 6101 Alloy Processed via ECAP-Conform

“…These precipitates point to the fact that the UFG structure formation during ECAP-C was accompanied by solid solution decomposition due to the dynamic aging (DA). It has also been previously observed in various Al-Mg-Si alloys during SPD both at elevated [19][20][21][22][23][24][41][42][43][44][45] and room temperature [23,24,46].…”

“…Additionally, nanoscale spherical metastable β′-second-phase precipitates were formed in the Al matrix during ECAP-C. Their morphological features are typical for Al alloys, since the formation of ultrafine grains in these alloys is accompanied by the decomposition of solid solution and the formation of strengthening Mg2Si phases [19][20][21][22][23][24][41][42][43][44][45][46]. Their spherical shape is different from the shape of β′-phase (in the form of spheres) formed as a result of a conventional thermal (of Т6 type) and/or thermomechanical treatment (of Т81 type) of CG counterparts [9][10][11][12][13][14].…”

Enhanced Strengthening in Ultrafine‐Grained Al–Mg–Si Alloys Produced via ECAP with Parallel Channels

“…[4,11,[14][15][16][19][20]22] Precipitates up to 20 nm are observed in the near-boundary area of the grain. These nanosized precipitates are defined as metastable b 0 .…”

“…These nanosized precipitates are defined as metastable b 0 . [4,11,[14][15][16][19][20]22] A fuller decomposition of the supersaturated solid solution takes place during ECAP processing. A lattice parameter measured by the XRD technique is found to be 4.05080 AE 0.0002 Åand 4.05170 AE 0.0002 Å, respectively.…”

Al/C60 Nanocomposites Fabricated by High-Pressure Torsion

“…where r 0 is the friction stress (20 MPa [15] ), k y is the Hall-Petch coefficient (0.04 MPa ffiffiffiffi m p [15] ), d is the grain size, a is a constant (0.93 [16] ), G is the shear modulus (25.8 GPa), b is the Burgers vector (0.286 nm), q is the dislocations' density (estimated by the line intercept method, [17] %5 9 10 14 m À2 ), m is the Taylor factor (3.06 [12] ), F is the diameter of fullerene (8 to 15 nm), and f is the concentration of fullerene (0.02). In this analysis, the role of dispersion of thin oxide layer initially present on the surface of gas-atomized Al powders has not been considered.…”