Cyclic Flaring and Sinking (CFS) as a New Severe Plastic Deformation Method for Thin-walled Cylindrical Tubes

Abstract

A novel severe plastic deformation method entitled cyclic flaring and sinking (CFS) is presented for producing ultrafine-grained thin-walled cylindrical tubes. CFS process includes two different flaring and sinking half-cycles. At flaring half cycle, the flaring punch with two stepped regions is pressed into the tube. Shear and normal tensile strains are applied as a result of the existence of shear zones and increase in the tube diameter. In the second half cycle, the tube is pressed to the sinking die that applies same shear strains and normal compression strain. The results indicate that the yield and ultimate strengths of the CFS processed Al tube significantly increases to 155, and 168 MPa, respectively from the initial values of 35, and 80 MPa. The elongation to failure decreases to about 15 % after three cycles from the initial value of 56 %. In addition, the hardness increases to ~38 Hv after ten cycles of CFS from ~23 Hv.