Experimental investigations on the process of forming functional microstructured blades from highly filled thermoplastic composites prepared with La(Fe, Si)(13) alloys

UHighly loaded polymer extrusion and forming processes are low-cost manufacturing processes which use continuous polymer profiles to elaborate magnetocaloric composites and 2D structured thin components and shape them into a wide variety of materials. The development of functional composites involves various requirements, specifications, and composite component designs. A composite must exhibit a high shear viscosity for polymer extrusion processing and permit extremely high loadings of solids to produce functional magnetocaloric properties which are equivalent to those of bulk materials. A composite material based on highly loaded magneto caloric composites was elaborated and investigated by using gas-atomised La(Fe, Si)(13) alloys. This appears to be useful in the fabrication of functional structured magnetocaloric components as regenerators or blade shapes. In the present study, composite elaborations were investigated with specific focus on the homogeneity and rheological behaviours for a powder size distribution between 13 and 143 mu m, solid loadings of 35%-65% by volume, and shear rates of 10(2)-10(3)/s. The binder used was based on different thermoplastic polymers with low melting temperatures, such as polypropylene or low-density polyethylene, to avoid dehydrogenation of the magneto caloric powders during the material-forming process. The shaping of structured blades by highly loaded polymer processing from the compounding to the forming process through the development of innovative processes and dedicated extrusion lines equipped with well-designed microstructured thin-blade-forming tools was studied. Thin structured blades of thickness 0.5 mm were obtained with micropatterns of width 200 mu m, with the maximal efficiency being 92%. The Curie temperature was determined from the powder stage to the mixing process and the final material shaping to validate the magnetocaloric properties and quantify the limits of the methodologies developed with different powders (the Curie temperature was adjusted to -21 and 23.5 degrees C). In this regard, the elaborated composite and the structured thin extruded component were characterised in terms of the homogeneity, magnetocaloric properties, and dimensional and geometric tolerances.