Experimental investigation on the effect of process variables for the quality characteristics of AA 2024 processed in cold extrusion

Abstract

Extrusion process has many applications in manufacturing industries due to its ability to produce products of high quality. Extrusion process can be classified into hot extrusion and cold extrusion. The cold forward extrusion is carried out at ambient temperature and  has the additional benefit of improved mechanical characteristics. The metarial is compressed under intense pressure through a die orifice with a specific shape during the extrusion process. This process is effected by a few process variables, including die angle, punch speed, and lubrication are in greater extent towards the extrusion force requirement, microstructure and the product quality. Hence, the present experimental work focuses on extrusion of circular billet to produce cylindrical rod. Studying the behaviour of the material and the importance of the input process parameters during the cold extrusion process is the primary goal of this work. The experiments are carried out with AA 2024 alloy because of its wide applications in navy and  aircraft structures.  The varying die angles (10°, 20° & 30°) as well as punch speed (1.6 mm/min, 3.2 mm/min and 4.8 mm/min) and lubricants (molybdium sulphide (MoS2), zinc stearate and grease) chosen as input parameters. The  out put responses of this extrusion process are extrusion force, displacement, time and surface roughness. Extrusion forces are calculated based on flow stress curves at the locations of greatest elastic deformation. The results shows that increasing the punch speed and die angle increases the extrusion force. The microstructure evolutions and grain refinement at different die angles are examined using electron back scatter diffraction analysis.  At 30° die angle, the microstructure showed grain refinement. It is also noted that the damage is significant at 30° die angle with a punch speed  above  4.8 mm/min.