The process of manufacturing discontinuously non-centric steel reinforced aluminum by means of co-extrusion has been examined. By this process semi-finished reinforced profiles can be fabricated for further treatment through forging techniques. Therefore, steel reinforcement elements consisting of E295GC were inserted into conventional aluminum billets and co-extruded into two different solid profiles; a rectangle one by an extrusion ratio of 10.1:1 and a round one by 4.8:1. The used aluminum alloy is EN AW-6060. The billet temperature as well as the ram speed were varied to investigate their influence on the position of the reinforcement elements inside the strand. The measurement was done by a video measurement system, called Optomess A250, after milling off the strand. The distances between the elements in longitudinal direction were nearly constant, apart from the rear part of the strand. The same was observed for the distance of the steel elements to the profile edge. This due to the inhomogeneous material flow in the transverse weld, related to the billet-to-billet extrusion. The rotation of the reinforcement elements occurs because the elements flow nearby the shear zone. Further, micrographs were made to investigate the embedding situation and the grain size distribution. The embedding of the reinforcement elements were good in the solid round profile, but in the rectangle profile were found some kind of air pocket. The grain size of the aluminum alloy close to the steel elements is much smaller than in the other parts of the solid round profile.

Aluminum matrix composite extrusions reinforced with wires made of high strength stainless steel represent an innovative material concept for lightweight structures. The use of reinforcing elements should improve the mechanical properties and the performance of lightweight structures. This study deals with the process chain of extrusion and die forging to manufacture steel-reinforced products. The production of discontinuously-reinforced, semi-finished aluminum profiles by co-extrusion is in focus on the extrusion part. The material flow is analysed in order to understand, and further to influence, where the steel-reinforcements are appear in the strand. For the forging part the extruded profiles are continuous-reinforced by means of steel wires as well as partially by means of steels elements. For the process design the geometry of the forging die cavity and the material flow are of vital importance. A Finite Element Analysis is carried out in order to predict the position of the elements in the forging parts depending on the position in the extrusions.

Three innovative extrusion processes for the manufacture of multi-material parts are discussed: co-extrusion of discontinuously steel reinforced aluminum profiles, composite extrusion of continuously steel wire reinforced profiles and composite rod extrusion. In the first two processes the embedded steel elements are not deformable while by composite rod extrusion both materials are deformable. By means of experimental and numerical analysis, the parameters that mainly influence the reinforcement ratio, the extrusion force as well as the material distribution are analyzed. On the basis of this, analytical approaches are deduced to describe the process limits for the technologies. The paper closes with examples of applications regarding the lightweight requirements as well as functional integrations by forming multi-materials.

No abstract

The present paper investigates the grain size evolution in aluminium alloys AA 6082 and AA 7020 during hot forward extrusion process. The aim of the present work is the definition and implementation of a predictive algorithm that is able to compute the evolution of the grain shape during the process within the finite element method code Deform. Extrusion experiments were performed at two levels: at reduced scale for investigating and identifying the predictive equations and at industrial scale for validating the developed algorithm. At small scale extrusion, a complete factorial plan was performed for two alloys at three different temperatures, three extrusion ratios and two ram speeds: the discards and extrudates from the experiments were quenched immediately in order to avoid any potential recrystallisation, hence allowing measurements of transitional processing steps. At the industrial scale, instead, the 7020 alloy was extruded with two different die designs, thus producing a 20 mm diameter round bar under different extrusion ratios and strain paths. Finite element simulations were initially validated over visioplastic investigations in order to establish an accurate computation of the material flow, then experimental and numerical results were coupled, thus allowing the definition of the grain evolution model that was successfully integrated and validated on industrial scale trials.