Springback properties of single- and poly-crystalline pure aluminum processed by severe plastic deformation

Abstract

A bending tester with an incorporated high-precision angle sensor was developed in this study. Pure aluminum single crystal and polycrystalline materials were used. Bending properties, especially the springback characteristics of materials as-received and fine-grained using AR and ECAP processes, were investigated. The springback characteristics are discussed based on various mechanical properties that were elucidated by tensile and hardness tests. Consequently, the following results were obtained. (1) AR and ECAP cold-processing refined grains of both single crystal and polycrystalline materials with almost no work hardening exhibited increased Vicker's hardness Hv without a decrease in elongation δ, at an equivalent strain ε of not less than 1.0. (2) The ECAP sample, which underwent many cycles of high strain processing, i.e., being subjected to large equivalent strain ε, indicated a large springback angle δSB. It also turned out that springback angle increased with an increment of δSB=0.1° per cycle of ECAP processing. (3) Both nECAP-s [110] and nECAP-p samples demonstrated a constant springback angle δSB, irrespective of equivalent strain ε at a bending angle of not less than δ=95°. (4) Fine-grained materials show a bigger springback angle δSB than as-delivered materials. Nevertheless, AR and ECAP samples, processed with different strain loading mode, showed little difference in the trend of spring back angle δSB against bending angle δ. (5) Steel materials over a wide range tend to indicate springback angle δSB in direct relation to the n value. However, fine-grained pure aluminum material of this study turned out not to conform to this trend. The result of this series can constitute fundamental data that are useful toward the establishment of a plastic deformation processing method of fine-grained materials.