Single-pass severe plastic forming to manufacture products with superfine functions

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We developed an extrusion process with a cross-sectional area reduction as 'single-pass severe plastic forming (S2PF)' process for producing ultrafine-grained plain carbon steels. We investigated the microstructure and mechanical properties of fine-grained 0.2% carbon steels extruded at 1100-600℃. Ultrafine ferrite grains with a grain size of 1.2 micro meter were generated at the surface of the materials extruded at 700℃. The materials extruded at 800, 700 and 600℃ were investigated by scanning electron microscopy, electron backscattering diffraction analyses, tensile tests and compression tests. Extrusion at 700℃, which is near the austenite-ferrite transformation temperature (Ar3), produced a material sample with a diameter of 5 mm, an average ferrite grain size of approximately 2 micro meters, a tensile strength of about 700MPa, a uniform elongation of about 15% and a good cold-forging property.An 'single-pass severe plastic forming (S2PF)' is then applied to the forming of composite material. Here, light-weight structural metal, Aluminum A6061, is used as the base metal and multi-walled carbon nanotube (CNT) is selected as the additional material. Uniformly-distributed 1wt% CNT in A6061 matrix is successfully manufactured by the extrusion process, which directly enables compaction and sintering at the same time utilizing 'single-pass severe plastic forming (S2PF)'. Electrical conductivity is measured and it is elevated up to 125% of the matrix base metal A6061.