Grain refinement and properties of ultrafine-grained AI, Mg and Ti alloys produced by equal-channel angular pressing with back-pressure

Resumo

Severe plastic deformation (SPO) techniques have been widely evaluated for the production of materiais with ultrafine microstructure with grains. Among these procedures, ECAP is an especially attractive one and quite a number of recent scientific and engineering publications are devoted to studying considerable plastic strain, in particular, the strain created by equal channel angular pressing (ECAP). The number of such works continues to grow, which is explainable in the first turn by the relative simplicity of the ECAP process and by the possibility of obtaining exceptionally fine grains of submicron size. This results in considerable improvement of the mechanical properties of the alloys. However, applications of ECAP can be restricted during processing of hard-to-deforrn and low-ductility materiais. It is known that in order to effectively refine the structure and achieve superior properties ECAP should be realized in several cycles. The high levei of accumulated strain can result in crack initiation and failure of samples, which is connected with non-conformance of ductility and the levei of specific pressures holding back the sample failure. The deformation capacity of the material improves at elevated temperatures. However, the recovery processes and microstructure recrystallization makes it difficull to achieve lhe maximum degree of refinement and extraordinary properties. One of the effective ways to enhance the deformability resource durin ECAP is to increase the hydrostatic pressure. (AU)