This study examines the deformation behavior and microstructural evolution of 6061 aluminum alloy processed through severe plastic deformation (SPD) via biaxial alternate forging. The objective was to evaluate both the alloy's formability limit and mechanical properties. Finite element (FE) analysis was conducted to simulate the biaxial alternate forging process, incorporating the strain-hardening coefficient and the number of forging passes. When the strain-hardening coefficient was set to 0, an average effective strain of approximately 440% was observed in a 4 mm diameter region at the core of the workpiece after eight forging passes. In contrast, with a strain-hardening coefficient of 0.2, the average effective strain under the same conditions decreased to about 300%. The FE analysis of the 6061 aluminum alloy estimated an average effective strain of 326% after eight passes, indicating a level of severe plastic deformation well beyond the elongation capacity of the initial material. Tensile testing revealed that after two passes, the material showed a gradual increase in strength with only a minimal reduction in elongation. Even after accumulating a significant strain of 326% through eight passes, optical microscopy displayed deformed grains and twinning structures, with no signs of recrystallization across all examined forging conditions.

A hybrid cladding technology was developed by combining direct energy deposition (DED) and ultrasonic nanocrystal surface modification (UNSM). This is an effective process to control the mechanical properties inside the metal-clad layer, but the scope to improve the internal properties is low. Therefore, in this study, the UNSM process was applied while heating at 300 and 600℃ to increase the effectiveness of this hybrid additive process. To validate the characteristics of this method, a study on the cross-sectional properties upon application of heating was conducted. Hybrid cladding at 300 degrees produced improvements- over a 40% larger area than the results at room temperature. At 600 degrees, the hybrid cladding improved mechanical properties over a larger area by nearly 2 times. In this study, the characteristics of the roomtemperature and the high-temperature hybrid cladding process were analyzed. The proposed method shows a high improvement effect and is a promising method to improve the internal mechanical properties of the cladded layer.