Al/Mg compounds produced by hydrostatic extrusion exhibit unique characteristics in terms of high strength and low weight, which are required in lightweight safety parts. The compound interface between the core and sleeve is a brittle intermetallic phase consisting of Al 2 Mg 3 and Al 12 Mg 17 . However, a certain plastic deformability is required for subsequent processing of the semi-finished product by forming. To obtain a basic understanding of the deformation behaviour of the interface, the Digital Image Correlation is used together with a new analysis procedure based on the approximation of the displacement field with polynomial functions. The procedure is first tested with a bending test. The specimens exhibit a remarkable deformation behaviour under bending at high temperatures, which is confirmed by the results of radial upsetting tests. Even under a multi-axle load, the interface maintains a full material joint, though fragmentation occurs, and a new secondary interface between the fragments can be observed. In addition, an evaluation of light microscopy images and Eulerian Hencky strain values at the interface, which are based on the Digital Image Correlation results, imply a connection between the strain and the boundary layer's appearance.
Due to the higher demand for energy efficient products, light-weight constructions have become more important in recent years. An innovative, hydrostatic extruded Al-Mg-compound used here combines the corrosion resistance of aluminium with the outstanding lightweight properties of magnesium. During the production process, a thin boundary layer is built between the two basic materials. Investigations on further hot forming processing revealed a good formability of these compounds despite the fact that the boundary layer splits into fragments during forging and a new secondary boundary layer is built when the basic materials between the fragments come into contact again during the continuous deformation. The aim of the research is now to investigate fragmentation depending on the deformation rate and boundary layer thickness, which increases during the heat-up process in preparation of forging. For this purpose, a channel compression test is used in conjunction with a special newly developed specimen shape. The metallographic evaluation of the boundary layer reveals a strong dependency of fragmentation on the deformation rate and the boundary layer thickness. With the aid of a numerical simulation, an individual critical stretch could be determined at which fragmentation starts, and provide guidance for an optimal forging process design.
Al/Mg compounds produced by hydrostatic extrusion exhibit unique characteristics regarding high strength and low weight, which are required by safety part applications in lightweight constructions. Between the two materials an interface in form of a brittle intermetallic phase consisting of Al2Mg3 and Al12Mg17 arises during the production process. However, a certain plastic deformability of the semi-finished product is essential for further forming processes. Even under multi-axle load during a radial upsetting process, the interface maintains a full material joint although a fragmentation and a new secondary interface between the fragments can be observed. Due to the evaluations of light microscopy images and Eulerian Hencky strain values at the interface, which are obtained with the help of the Digital Image Correlation, a relation between the strain and the boundary layer's appearance seems reasonable.
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