Magnetic Properties and Microstructure of a FeCo Ferritic Steel after Severe Plastic Deformation

Abstract

A commercial FeCo ferritic steel with an initial grain size of 10 μm was subjected to Severe Plastic Deformation in a temperature range between 293 K (0.16Tm, Tm: melting temperature in K) and 723 K (0.4Tm) up to strain levels where a saturation of the microstructural refinement is observed. The microstructure of the severely deformed state is analyzed by Back Scattered Electrons micrographs captured in a SEM. The magnetic properties were characterized by means of SQUID-magnetometer providing information about the magnetization behavior of the material in the as processed state. Depending on the deformation temperature mean microstructural sizes in the steady state of 50 nm and 270 nm were observed after SPD at 293 K and 723 K, respectively. These small microstructural sizes influences significantly the magnetic properties of the material: it shifts the behavior from soft-magnetic in the initial coarse grained state towards a hard-magnetic with decreasing size of the crystallites. For sizes of the crystallites smaller than about 100 nm the magnetic properties become again more soft-magnetic.

Producing bulk ultrafine-grained materials by severe plastic deformation

“…Another example is SPD-processed magnetic materials such as Fe-Co. 53 Not only does the nanometer grain size induce advanced mechanical properties but it leads also to enhanced soft magnetic properties due to an interaction of magnetic moments across the grain boundaries in these materials. Thus, the engineering of multifunctional materials is rapidly becoming a new direction in the science of SPD nanomaterials.…”

In -Situ Annealing of Severe Plastic-Deformed OFHC Copper

“…Such a behavior is well known to occur at large deformations at warmand hot-working conditions due to discontinuous [34,35] or discontinuous dynamical recrystallization. [9,[36][37][38][39] Recently, it was reported for pure copper, a-iron, and single-phase steels [7,20,27] that a steady state is reached even during severe plastic deformation at low homologous temperatures. A restoration mechanism similar to dynamic recrystallization, [27] and, more specifically, geometric dynamic recrystallization, [20] was proposed to be sufficient to provide such a steady state.…”

“…[1][2][3][4][5][6][7] Besides the conventional methods for producing such fine microstructures, such as rapid solidification, powder metallurgy, and vapor condensation methods, [8] it is now well established that nano-or at least submicrometer-grained microstructures can also be obtained by applying large strains at low homologous temperatures to metallic materials. [3,9,10] Many different techniques for severe plastic deformation are known, [11][12][13][14] which all provide nearly infinite strains without failure of the material.…”

The Innovation Potential of Bulk Nanostructured Materials

“…[49] Such a combination in the TiNi alloy is in stark contrast to its conventional coarse-grained counterpart. Another example is SPD-processed bulk magnetic materials such as Fe-Co. [50] Not only does the nanometer grain size of these materials induce advanced mechanical properties but it leads also to enhanced soft magnetic properties due to the interaction of magnetic moments across the grain boundaries. Thus, the engineering of multifunctional materials is rapidly becoming a new direction in the science of SPD nanomaterials.…”