Influence of Coating Thickness on the Formability of Annealed Aluminum 2024

Sheet metal forming of uncoated Aluminum 2024 (Al-2024-TO) alloy was performed on conventional press with a movable punch. A set of four uncoated aluminum specimens (UCS) was formed after the application of silicone-based lubricant on the specimen surface facing punch. Variation in thickness of the specimens at different locations was one of the major concerns during forming operation which caused localized thinning and hardening of stock, resulting in a premature fracture (100 mm depth). Thin porous membranes were deposited on the specimens to enhance lubrication (by retaining the lubricant) and reduce friction between clamp and stock. Four sets of coated specimens (CS) with different film thicknesses (5 μm, 10 μm, 15 μm, and 20 μm) were anodized and formed to study the effect of coating thickness and lubricant entrapment on the formed depth. Characterization of coated specimens operation exhibited that the porous thin film with an optimum thickness of 10 μm (pore diameter of 60-68 nm) facilitated the maximum entrapment of lubricant in the pores. Enhanced lubrication for CS-2 resulted in the aggravated material flow which showed minimum hardness (60 HV), minimum thickness variation (2.82-2.90 mm), and minimum draw force (11 kN) with the maximum draw depth of 172 mm.