Finite element analyses of extrusion with a two stage die and manufacturing of gradient micro-structures

This paper aims to manufacture aluminum alloy metals with gradient micro-structures using hot extrusion process. The extrusion die is designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. At first, temperature, effective strain, and effective strain rate distributions at the die exit are discussed for different inclination angles in the conical die using the finite element analysis. Then, hot extrusion experiments are conducted to obtain aluminum alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products are also discussed.