Formability of Hybrid Aluminum-Magnesium Compounds

Abstract

In the SFB 692 HALS (High-strength aluminum based lightweight materials for safety components), subproject B-3, the production of an aluminum magnesium compound by a hydrostatic co-extrusion process was investigated. The quality of these semi-finished products, especially the stability and robustness of the interface between the aluminum (AlMgSi1) sleeve and magnesium (AZ31) core, was of particular interest. Previous papers have described the first process optimization steps as the improvement of the die design as well as the numerical methods for identification of important process parameters and the development of a quality model for the interface. This paper describes the formability of such semi-finished products with subsequent forging processes, especially die forging. Therefore, two different die forging strategies were investigated. In the first approach the strand-shaped work piece, with a circular cross-section, was formed along its longitudinal axis with die forging. In the second approach the same geometry was radially formed with die forging. Thereby, the compound was formed in longitudinal direction up to an analytical equivalent strain value of 1.61 and in radial direction up to 1.38. First results showed that the interface of the aluminum magnesium compound is very stable and ductile enough to be forged. Dye penetration tests were performed to prove the stability of the interface in a first step. Then, micro sections were made to investigate the interface metallographically. No cracks or damages were detected with both test methods in the interface of the forged aluminum magnesium compound. Furthermore, numerical simulations were performed to analyze the forging processes in detail. Therefore, a full 3D simulation model was set-up with Forge2011 and the calibration was performed with the press force as well as the geometry aspects. The correlations between experiments and simulations are very well. By means of the calibrated simulation detailed analyses of interface section are performed and the stability of the interface was investigated. This shows that the compound quality reached by the hydrostatic co-extrusion process is very suitable for subsequent forming steps as die forging. The investigations show the potential of such hybrid compounds and clarify their application, especially in the automotive sector.

Process Chain for the Production of a Bimetal Component from Mg with a Complete Al Cladding

“…They used continuous reinforcement only for co-extrusion and discontinuous for forging, and produced a component with different distributions of the wire reinforcement [22]. This was confirmed by Feuerhack [23], who investigated the processing of co-extruded Al-Mg rods by die forging. It was shown that the interface remains intact if compression stresses dominate.…”

“…It was shown that the interface remains intact if compression stresses dominate. Shear stresses caused a fragmentation of the interface, but a new interface was built between the fragments [23].…”

“…Based on experimental investigations, a Tresca friction factor of 0.2 was used to model the lubrication conditions. parameters identified by Feuerhack [23,28]. The models can be seen in Figure 4 [28].…”

“…He used the simulation system FORGE by Transvalor with implicit time integration. The software was also used for the forging processes in the present investigation based on the process parameters identified by Feuerhack [23,28]. The models can be seen in Figure 4.…”

Interface Engineering of Aluminum-magnesium Compounds

“…It could be confirmed that the interface between the two materials consists of two intermetallic phases β (Al3Mg2) and γ (Al12Mg17) with significantly lower ductility than the basic materials [2]. The realization of a component with a complete interface out of the extruded strands was successfully demonstrated by FEUERHACK et al [3,4,5]. He used forging to produce a complex demonstrator component as shown in Fig.…”