The microstructure, mechanical properties, and strengthening mechanisms of an Al-Mg-Si alloy (AA6060) subjected to severe plastic deformation using equal channel angular pressing (ECAP) were investigated. Samples were passed through a die with an inner angle of F = 90° and outer arc of curvature of ¿ = 37° at room temperature up to 12 passes via route Bc. Electron backscatter diffraction (EBSD) was used to evaluate the microstructure and misorientation boundaries. The microstructure showed a large fraction of low-angle boundaries associated with subgrain formation in the first ECAP pass, while after eight and 12 passes, a heterogeneous ultrafine grain structure with an average grain size around 0.57 and 0.47 µm, respectively, was obtained. In order to characterize the mechanical properties, microhardness and tensile tests were carried out. Results of mechanical property tests show that microhardness, yield stress, and ultimate tensile strength increase as ECAP pass number increases up to a maximum value of 120 HV, 344 MPa, and 355 MPa, respectively, after five passes. The Hall–Petch effect, dislocation, solid solution, and precipitation strengthening were evaluated to determine the dependence of the yield stress on the ECAP pass number. The results show that the strength effect arises from the subgrain microstructure rather than from the high-angle grain boundaries developed.Peer ReviewedPostprint (published version

An AA6082 alloy deformed by equal channel angular pressing (ECAP) was studied. The evolution of microstructure as a function of the strain imparted was evaluated by optical microscopy (OM), scanning electron microscopy (SEM) coupled with an electron backscattered diffraction (EBSD) detector, X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). XRD showed that MgSi2 precipitates developed in the ECAPed specimens. Texture analysis showed the apparition of two types of textures, one associated with shearing deformation and the second due to the recrystallization phenomena. Mechanical strength properties measured by tensile tests increased in the first ECAP pass, and then progressively diminished. This phenomenon was associated to the activation of continuous softening phenomena. Calorimetric analysis indicated a slightly rise in the recrystallization temperature of the deformed specimens. Also, the stored energy increased with rising ECAP passes due to the production of new dislocations. The average geometrically necessary dislocation (GND) density, measured by EBSD, increased with increasing ECAP passes. However, the rate of increase slows down with the progress of ECAP passes.

Strain hardening is a useful mechanism for improving mechanical properties in materials. This study investigates the strain‐hardening behavior of an AA6060 alloy processed by equal channel angular pressing (ECAP) up to 12 passes. Analysis by electron backscattered diffraction (EBSD) shows that the average geometrically necessary dislocations (GNDs) density increases continually up to the fourth pass and then saturates at a value of ≈1.85 × 1014 m−2. Hollomon and Kocks–Mecking–Estrin (KME) analysis are used to investigate the strain‐hardening behavior of the resulting ultrafine‐grained alloy. Results indicate that the strain‐hardening capacity (HC) and the strain‐hardening exponent (n) of all deformed specimens are lower in comparison with the as‐received condition. Moreover, the strain‐hardening rate fluctuates with the ECAP passes. First, it increases from the first ECAP pass up to the fourth pass, then diminishes up to the fifth pass, and finally, it increases again with further deformation. The difference in the strain‐hardening behavior of the ECAPed AA6060 is examined in terms of the grain size effect. It is shown that the strain‐hardening curves change notably with diminishing the grain size. In addition, the KME model is used to depict the storage and annihilation of dislocations in the ECAPed specimens.

The powders of the AA 7075-ZrO 2 were mixed by mechanical milling, but it was found that the system presents a few disadvantages when processed by conventional sintering and hot extrusion, since intermetallic phases between ZrO 2 particles and alloying elements were formed. Equal channel angular pressing (ECAP) processing was proposed as an alternative method to consolidate the composite where there is no intermetallic formation. The analysis of the ECAP process showed that the intermediate temperature (220°C) produced a higher consolidation level than conventional sintering and hot extrusion (400 and 500°C, respectively). This fact was supported by relative density analysis. In the case of the sintered and hot-extruded sample, the relative density exhibited a value of 0.95, while ECAP sample showed a value of 0.98. Hardness values show that microstructural refinement obtained during mechanical milling was preserved during ECAP processing even when it was carried out at 220°C.