Comparison of cast and extruded stock for the forging of AA6082 alloy suspension parts Yucel Birol 1, a , Onur Ilgaz 2, b , Seracettin Akdi 2, c and Erdem Unuvar 2, d 1 Materials Institute, Marmara Research Centre, TUBITAK, Gebze, Kocaeli, Turkey 2 R&D Centre, AYD Steering and Suspension Parts, Selcuklu, Konya, Turkey a yucel.birol@tubitak.gov.tr, b ilgaz.onur@ayd.com.tr, c akdi.seracettin@ayd.com.tr, d unuvar.erdem@ayd.com.tr Keywords: Aluminium alloys; Forging; Heat treatment. Abstract. High-precision near-net shape parts with excellent surface qualities can be produced with the forging process with a minimum of finishing operations thanks to the good formability of aluminium alloys. There has been a rapid increase in the use of aluminium forgings predominantly in the automotive industry, where weight savings for reduced fuel consumption and exhaust emissions is mandated by legislation. Aluminium forgings provide, in addition to low weight, high strength, good corrosion resistance and a fibrous grain structure to improve fatigue resistance. Typical commercial forging stock is the round bars produced by the extrusion of cast billets. An alternative process route that has received increasing attention in recent years is the casting of forging stock by a horizontal direct chill casting technique to make smaller billets without the need for extrusion to reduce their diameter. The anisotropy imparted to the forging stock via extrusion, often regarded as useful for the forging, is certainly missing in the former. However, cast stock has been reported to be more resistant to the formation of coarse surface grains than the extruded counterpart. The present work was undertaken to compare the casting and extrusion routes for the manufacture of 6082 alloy forging stock. Introduction Forging is a near-net shape manufacturing process where metal is pressed, pounded or squeezed under high pressure into high performance components [1]. Forgings offer higher strength and ductility with respect to cast and machined parts, owing to an improved soundness and uniformity in chemistry. Additionally, forged components enjoy a favourable grain structure that can be oriented in the direction of principal stresses encountered in service with a proper selection of starting material, die design and process parameters [2]. Hence, forgings are better suited for those structural applications where reliability and human safety are critical. The ever increasing need for lightweight solutions in the transportation industry give aluminium forgings a considerable edge [3]. There has been a rapid increase in the use of aluminium forgings particularly in the automotive industry, where weight savings for reduced fuel consumption and exhaust emissions is mandated by legislation. In addition to light weight, aluminium forgings provide high strength, good corrosion resistance and fatigue resistance. Thanks to the outstanding formability of aluminium alloys and to the development of modern, efficient presses, it is possible to produce high-precision aluminium parts that fully conform to the strict requirements of the automotive industry with only a minimum of additional finishing operations. High performance aluminium parts such as suspension arms and steering columns have thus become standard in most passenger cars. The characteristic feature of aluminium alloy forgings is a dense fibrous microstructure achieved by properly designed material flow that is governed by the extent and rate of deformation and temperature [3]. Optimum mechanical properties, i.e. strength, ductility, toughness and fatigue, are obtained in the fibre direction. However, friction and high shear strains in the contact zone between the work piece and the die can lead to a recrystallised surface layer that often degrades the service performance of the component.