Study on processing and structure property of Al-Cu-Mg-Zn alloy cup-shaped part produced by radial-backward extrusion

Abstract

In this work, three cavity structures of radial-backward extrusion (RBE) have been employed to produce Al-Cu-Mg-Zn alloy cup-shaped part. The effects of the cavity structure on the average effective strain, forming load, and forming damage of cup-shaped part produced by RBE were investigated by finite element simulations, and then the influences of frictional coefficient and ram speed on the forming damage were also studied. Comparisons of mechanical properties and microstructure between cup-shaped part produced by RBE and by traditional backward extrusion (TBE) were conducted by experimental works. The finite element simulation results show that the minimum average effective strain and maximum forming damage were acquired in RBE with type-A cavity (RBE-A); the maximum average effective strain and minimum forming damage were obtained in RBE with type-B cavity (RBE-B), and the forming damage and average effective strain were moderate if RBE with type-C cavity (RBE-C) has been used. For RBE-A, RBE-B, and RBE-C, the forming damage decreases as ram speed increases or frictional coefficient decreases. With the identical frictional coefficient and ram speed, the forming load increases in an order from type-A cavity, type-C cavity, and type-B cavity. The average effective strain in RBE-C is about 1.9 times of that in TBE. The uniform degree of deformation in RBE-C is far better than that in TBE. The experimental results show that after RBE-C, ultimate tensile strength and yield strength of tube length of formed part are significantly larger than that after TBE, and ultimate tensile strengths and elongation of tube length are around 349 MPa and 22%, respectively. Better refinement of grain and more uniform distribution of strengthening phase can be achieved by RBE-C than by TBE.