By now it is well established that severe plastic deformation (SPD), i.e intense straining under high imposed pressure has an ability in either strongly refine microstructure till up nanometer range and change essentially a phase composition forming highly metastable states in bulk samples of various alloys. Therefore, there is a potential to achieve a new and extraordinay properties. However, attaining such properties is complex problem, which depends on different processing and microstructural parameters. This paper focuses on SPD processing by severe torsion straining of several Ti, Al and hard magnetic Pr2Fe14B based alloys. It is shown that for SPD microstructures it is typical to have a presence of not only a very small grain size, but also specific defect structures, high internal stresses and often a formation of supersaturated solid solutions and amorphyzation of intermetallics phases in these alloys. During further heating ageing effects and reordening take place and processed alloys demonstrate unique mechanical (strength and superplasticity) and magnetic properties.
|