Sandwich rolling of twin-roll cast aluminium-steel clad strips

In the present study experimental results of twin-roll cast aluminium-steel clad strips of a thickness of 2.0 mm using the example of pure aluminium and an austenitic steel are presented. Electron probe measurements of the bonding area revealed the presence of a continuous interface layer of about 2 μm. To verify the formability of the twin-roll cast clad strips, sandwich samples were cold rolled with up to 66% strain. Furthermore, the sandwich samples were hot rolled at the temperature of 300 °C with different strain values. Mechanical properties, the microstructure and the surface quality of the deformed compound after rolling were analysed. To test ductility and formability of the rolled strips these were cold deep drawn.DFG/SCHA1484/21-

New Twin-Roll Cast Al-Li Based Alloys for High-Strength Applications

Al-Li based alloys are attractive materials for the aerospace industry. The twin-roll casting of such materials could provide properties not achievable by conventional direct-chill casting and downstream processing methods due to significantly higher solidification rates. An Al-Li-Cu-Mg-Zr alloy was twin-roll cast with the same alloy containing a small addition of Sc. The microstructure of as-cast materials and the influence of Sc on the behavior of the alloy at elevated temperatures were studied by means of light and electron microscopy and by resistivity measurements. A fine-grained structure was formed during twin-roll casting, but several surface and internal defects were found on the strips, which should be suppressed by a further adjustment of the casting conditions. The addition of Sc had a positive effect on grain size uniformity and microstructure stabilization at elevated temperatures, as shown by the precipitation of a fine dispersion of coherent Sc- and Zr-containing precipitates

Effect of Solidification Rates at Sand Casting on the Mechanical Joinability of a Cast Aluminium Alloy

Implementing the concept of mixed construction in modern automotive engineering requires the joining of sheet metal or extruded profiles with cast components made from different materials. As weight reduction is desired, these cast components are usually made from high-strength aluminium alloys of the Al-Si (Mn, Mg) system, which have limited weldability. The mechanical joinability of the cast components depends on their ductility, which is influenced by the microstructure. High-strength cast aluminium alloys have relatively low ductility, which leads to cracking of the joints. This limits the range of applications for cast aluminium alloys. In this study, an aluminium alloy of the Al-Si system AlSi9 is used to investigate relationships between solidification conditions during the sand casting process, microstructure, mechanical properties, and joinability. The demonstrator is a stepped plate with a minimum thickness of 2.0 mm and a maximum thickness of 4.0 mm, whereas the thickness difference between neighbour steps amounts to 0.5 mm. During casting trials, the solidification rates for different plate steps were measured. The microscopic investigations reveal a correlation between solidification rates and microstructure parameters such as secondary dendrite arm spacing. Furthermore, mechanical properties and the mechanical joinability are investigated

Numerical Analysis of Twin-Roll Casting of Strips With Profiled Cross-Section

<div><p>The relatively high production costs of innovative materials with tailored properties such as Tailor Welded Blanks, Patchwork Blanks, Tailor Heat Treated Blanks and Tailor Rolled Blanks are responsible for a growing interest in new cost-effective production methods. One of the promising energy-saving and environmental friendly technologies for the production of tailored blanks is twin-roll casting. In the study a new alternative method for twin-roll casting of strips with profiled cross-section is proposed, which uses one or more preloaded endless steel strips with an antiadhesive coating for profiling of the formed strip on a pair of the common cylindrical shells. As a primary stage for the practical process design, numerical simulation of the process using the finite element software package ANSYS is realized. In this way, dependencies of the strip elements outlet temperature, deformation zone length and elements outlet speed on the varied strips thickness and total solidification-deformation zone length are established. Based on the simulation results, a procedure for the twin-roll casting process design is suggested.</p></div

Roll Bonding of Steel Net-Reinforced Aluminium Strips

<div><p>The present study is dedicated to the experimental determination of strain parameters at rolling of aluminium matrix with inserted wire netting. Two types of stainless steel fabric netting with different orientation to the rolling axis were placed between two aluminium strips and hot rolled. The rolling temperature and reduction were varied to achieve the sound bonding between the matrix layers and steel net. During the study, the following main investigations were made: strain on areas of longitudinal and transverse cross sections of the composite was measured; stretching and ovalization of net wiring and changes in the net cell angles were determined; mechanical properties of composites along the rolling direction were tested. The experiments were summarized by following contradiction: the contact pressure, required for the bonding of aluminium layers, produces extreme tensile strain on the inserted wires, reducing the mechanical properties of the reinforcing net and, consequently, reducing the properties of the entire composite. Strips with diagonally oriented reinforcing net showed the best results in the longitudinal tension tests.</p></div