MICROSTRUCTURE AND PROPERTIES OF COPPER AND ALUMINUM-ALLOY-3003 HEAVILY WORKED BY EQUAL CHANNEL ANGULAR EXTRUSION

A technique invented in the former Soviet Union and recently introduce d in the United States, called equal channel angular extrusion (ECAE), produces intense and uniform deformation by simple shear and is appli ed to 25 X 25 X 152-mm billets of Cu 101 and Al 3003. Microcrystalline structures with a grain size of 0.2 to 0.4 mu m are created during ro om-temperature multipass ECAE deformation for true strains lying in th e range epsilon = 2.31 to 9.24. Evidence shows that intense simple she ar deformation promotes dynamic or continuous recrystallization by sub grain rotation. The effects of the number of extrusion passes and defo rmation route for Cu 101, and the deformation route after four passes for Al 3003, are studied. Increasing the number of ECAE passes in Cu 1 01 causes strength to reach saturation and grain refinement stabilizat ion after four passes (true strain of 4.68), and subgrain misorientati on to increase as the number of passes increases. For multipass ECAE w ith billet orientation constant (route A) or rotated 90 deg between al l passes (route B), two levels of structures are created inside the or iginal grains: shear bands (first level) and very fine subgrains (seco nd level) within the shear bands. For a billet rotation of 180 deg bet ween passes (route C), an unusual event is observed. At each even numb ered pass, shear bands nearly disappear and only subgrains are present inside the original grains. Route B gives the highest strength, where as route C produces a more equiaxed and stable microstructure. Subsequ ent static recrystallization increases the average grain size to 5 to 10 mu m.