Papers by Author: Alfred V. Sharafutdinov

Abstract: In the present work high pressure torsion (HPT) was imposed on commercial purity (CP) tungsten at different temperatures of 450 °С and 490 °С to achieve different microstructures and grain boundary misorientation spectra (GBMS). After HPT at 450°С, ultrafine grained microstructure with an average grain size of ~150 nm was developed in the metal. HPT at 490 °С results in an elongated structures with average width of ~500nm. EBSD investigations showed that over 92% are HAGB type in microstructure HPT-processed at 450°С, and in contrast, over 50% of grain boundaries are LAGB in sample processed at 490°С. Annealing at 900°С for 1h, of the sample with homogeneous UFG structure resulted from HPT at 450°C, leads to only limited decrease (~20%) in microhardness.

Abstract: The structure and mechanical properties of Al-based alloy 2024 after high-pressure torsion (HPT) was investigated. Alloy 2024 with homogeneous structure and grain size about 70 nm was obtained using HPT at 6 GPa pressure and 5 turns of the anvils at room temperature. The nanostructured alloy possessed very high UTS (Ultimate tensile stress) above 1100 MPa at room temperature, and superplastic behaviour at temperatures over 300°С. The microhardness of the nanostructured alloy after superplastic deformation (1.5 GPa) was greater than that after the standard treatment of the coarse-grained alloy (1.2 GPa). The influence of HPT parameters and heat treatment on the structure and deformation behaviour of the alloy was studied. The opportunity of achieving a combination high strength and good ductility in metals and alloys opens perspectives for industrial applications, particularly, in micro-systems and for high-strength items with complex geometry which could be obtained by superplastic forming.