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

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An ultrafine grained Al-Mg-Si alloy was prepared by severe plastic deformation using the Equal Channel Angular Pressing (ECAP) method. Samples were ECAPed through a die with an inner angle of Φ=90º and outer arc of curvature of ψ= 37° from 1 to 12 ECAP passes at room temperature following route Bc. To analyze the evolution of the microstructure at increasing ECAP passes x-ray diffraction and Electron Backscatter Diffraction analyses were carried out. The results revealed two distinct processing regimes, namely: i) from 1 to 5 passes, the microstructure evolved from elongated grains and sub-grains to a rather equiaxed array of ultrafine grains and ii) from 5 to 12 passes where no change in the morphology and average grain size was noticed. In the overall behavior, the boundary misorientation angle and the fraction of high-angle boundaries increase rapidly up to 5 passes and at a lower rate from 5 to 12 passes. The crystallite size decreased down to about 45 nm with the increase in deformation. The influence of deformation on precipitate evolution in the Al-Mg-Si alloy was also studied by differential scanning calorimetry. A significant decrease in the peak temperature associated to the 50% of recrystallization was observed at increasing ECAP passes.

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A Fe-48wt%Ni alloy was processed by severe plastic deformation using equal channel angular pressing process. A stacking of 9 sheets was introduced and pressed up to two passes into die with an inner angles of Φ=90º and outer arc of curvature ψ= 17° at room temperature following route A. The same material in bulk form was also ECAPed up to one pass. The microstructure and the texture were investigated by means of electron backscattered diffraction and X-ray diffraction, respectively. To evaluate the mechanical response, Vickers microhardness was carried out. The given analyses concern the asreceived sample, the peripheral and the central plates of the pressed stacks and the upper, the middle and the lower parts of the pressed bulk material. The deformation was heterogeneous and variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally noted. For the stacks samples, the microstructure evolved from equiaxed grains of 9 μm with high fraction of high-angle grain boundaries (around 90%) to a heterogeneous fine grain structure with an average grain size of 3 m after two passes. On the contrary, for the bulk sample, the evolution was 2 to a banded structure after one pass. Results of mechanical property show that microhardness increased significantly from 147 Hv before deformation to mean values of 244 (after one pass) and 235 Hv (after two passes) for the bulk and stacked samples, respectively. The Hall-Petch effect and dislocation density were evaluated as the most responsible in material strengthening.

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Introduction: Squamous cell carcinoma of the conjunctiva is generally a low-grade tumor. Invasive squamous cell carcinoma, however, is uncommon, and intraocular extension has rarely been reported. We report a case of invasive squamous cell carcinoma of the conjunctiva with intra-ocular involvement in 94 year-old man. Methods: A case report. Results: A 94-year-old male patient presented with a rapidly growing exophytic mass involving the right eyeball for 2 months.The biopsy performed a well differentiated squamous cell carcinoma of the conjunctiva. The extension assessment showed local bone extension. The patient underwent exenteration with good postoperative consequences. Conclusion: This disease has a variable appearance. Late presentation with large orbital tumours are not uncommon. Early diagnosis is crucial to improve the visual prognosis.

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