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

为了生产超细晶粒普通碳钢，我们开发了一种横截面压缩的挤压工艺--单道次强塑性成形(S2PF)工艺。研究了细晶0.2%碳钢在1100-600℃挤压条件下的组织和力学性能。在700℃挤压条件下，材料表面生成了尺寸为1.2微米的超细铁素体颗粒。用扫描电子显微镜、电子背散射衍射仪、拉伸试验和压缩试验对800、700和600℃挤压后的材料进行了研究。在接近奥氏体铁素体转变温度(AR3)的700℃挤压条件下，获得了直径为5 mm、平均铁素体晶粒度约为2微米、抗拉强度约为700 MPa、均匀延伸率约为15%、良好的冷锻性能的材料样品，并将其应用于复合材料的成形。这里，使用了轻质结构金属铝A6061作为母材，选择了多壁碳纳米管(CNT)作为辅助材料。采用挤压法制备了均匀分布于A6061基体中的1wt%碳纳米管，直接实现了压实与烧结同时进行的“单道次强塑性成形(S2PF)”。测量了电导率，并将其提高到基质母材A6061的125%。

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.