No abstract

No abstract

No abstract

No abstract

Magnesium alloys based on MgAlZn system are very attractive materials in many industries due to their specic properties. One of common forming manners suitable for this kind of material is the application of severe plastic deformation method. This paper is focused on the deformation behavior of AZ63 alloy at equal channel angular pressing process in the temperature range of 250320• C. For this purpose nite element analysis was used. Main attention was devoted to the inuence of processing parameters on the material ow. Among other, changes of the ow during equal channel angular pressing in chosen regions of the pressed samples were monitored. As variables, temperature, friction coecient, strain rate, φ-angle or back pressure application were chosen. The comparison of the material ow lines at dierent conditions shows the aecting of material ow. There are obvious considerable dierences between regions adjacent to the inner radius and those adjacent to the outer radius. For example in the case µ = 0 the dead zone is delimited by the angle Ψ = 36• , while in the case of friction given by the coecient µ = 0.04, the value of the angle was Ψ = 26.5• .

The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdHx. Composition inhomogeneity in the Nd2Fe14B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment.

No abstract

No abstract