Effects of lubricant on the mechanical properties of aluminum 6063 alloy after ECAE

Purpose – The purpose of this paper is to investigate the degree of improvement in mechanical properties of aluminum alloy (AA6063) after processing with equal channel angular extrusion (ECAE) using four environmentally benign lubricants. Design/methodology/approach – Aluminum (Al) 6063 bar was annealed at 350°C for 1 hour, machined and cut to billets measuring 14 × 14 × 44 mm3. These specimens for extrusions were machined to the specified dimension to a visibly good finish. The billets were extruded through ECAE die of 14 × 14 mm2 channel cross-section area; the channel angle was 120°; and the angle of the outer arc of the channels was 30°. The punch and container used for the experiment were made of tool steel alloy AISI D2, and were chromium-coated and polished. Four lubricants such as palm, olive, coconut and groundnut oils were used in this study. Findings – The yield, ultimate tensile strengths (UTS) and the ductility of the material ECAEed with palm oil as lubricant, which gave the least extrusion pressure, produces the maximum yield, UTS and ductility, followed by groundnut oil and coconut oil, while olive oil gave the least yield strength, (UTS) and ductility. However, palm oil and olive oil have better load reduction than other lubricants. Furthermore, from the hardness results, though scattered, all of the points at the tensile strained side of the extrudate lie within a reasonably narrow band, suggesting a high degree of homogeneity and greater hardness value within the rod than the compressive side after being ECAEed. Originality/value – It is shown in the paper that all the lubricants tested greatly enhanced mechanical properties of Al 6063 and can effectively replace the petroleum-based lubricants used in forging operations.