| Popis: |
A multi-pass equal-channel angular pressing (helical channel angular pressing-parallel channel, HCAP-PC) is proposed to enhance process efficiency and avoid plastic deformation damage during the preparation of ultrafine-grained age hardened aluminum alloys. Multiple shear and twist deformations are provided at the single extrusion channel. The channel parameters were optimized by using grey relational analysis (GRA). An orthogonal L16-4-5 test array containing five factors (ψ, ϕ, γ, m and the length of L1 section) and four levels was collected to investigate the influence of channel parameters on the effective strain, the effective stress, the amount of damage and the deformation homogeneity coefficients. Based on the GRA, the grey relational coefficients and the grey relational grades were calculated to report the significant channel parameters which affect the extrusion quality and efficiency. Furthermore, according to the results of segregated grey relational grades, the contribution orders from high to low were listed as ψ, ϕ, γ, m and L1. The extrusion experiments were carried out with aluminum alloy 2024 after solid solution treatment and at the HCAP-PC die with geometry of ψ 20°, ϕ 90°, γ 73°, m 1.35 and 1d. The ultrafine-grained age hardened aluminum alloys were prepared and the process time was decreased to less than 120 min. |
