Transport industry faces challenges steadily due to rising fuel costs and stricter regulations for the emission of air pollutants. Technological developments that reduce fuel consumption are necessary for sustainable and resource-efficient transport. Innovative production technologies utilising multi-material designs come to the fore in an attempt to fabricate lightweight products with extended functionality. Departing from this motivation, novel process chain concepts for the manufacturing of bi-material forged products are being researched at the Leibniz Universität Hannover in the context of the Collaborative Research Centre (CRC) 1153. The developed technology is referred as Tailored Forming and deals with the deformation and subsequent processing of joined hybrid workpieces to produce application-oriented products. Deformation processes are carried out at elevated temperatures for thermomechanical treatment of the joining zone properties. Researchers make use of numerical simulation in each step in the process chains. This paper explains the challenges associated with induction heating and impact extrusion of bi-material forging billets and presents our solution approaches with the aid of numerical modelling. Experimental validation results and analysis of deformed workpieces are also shown.
Lubrication is essential in metal forming processes. As an example, it has a significant effect on the extent of homogeneity of forming and the resulting component surface. Thus, an adequate lubrication technique is required for a consistent part quality. In this contribution a new lubrication approach for cold bulk metal forming is presented. By exploiting the process-related porosity of powder metallurgical (PM) components as a lubricant storage, the resulting pressure of a forming process forces the stored oil to leak out lubricating the process. As a result, advantages like a decrease of process time because of the omission of the additional lubrication step, and an increased deformability due to compensation of lubricating film break are expected. Besides that, the porosity of the PM component is reduced leading to improved mechanical properties. Experimental investigations with cylindrical PM components were carried out by compression tests in dependence of initial porosity, impregnation time and lubricant. It was found that the required maximum load is reduced by up to 39 % by applying the new lubrication method. In addition, relative densities up to 99 % are reached after deformation.
By applying vibrations to a granular media differing in size and density, various segregation states can be established. If an additional rotational motion is engaged, the effective force is no longer gravity but a centrifugal one, leading to a radial segregation. In this contribution, an experimental setup is presented which utilizes these effects. This setup is used to produce a cylindrical metal matrix composite consisting of silicon carbide and aluminium having a radial gradient. The influence of different material- and process-specific parameters on the segregation behaviour was investigated. The evaluation of micrographs of the pressed and sintered samples shows that both positive and negative gradients can be achieved. The rotation speed and the grain size ratio were identified as significant factors. The variation of the vibration amplitude leads to opposite effects. On the one hand, the gradient intensity increased. On the other hand, the variances of the SiC distribution in the tangential or radial directions increased as well. In addition, it has been shown that the effects of different grain shapes are marginal.
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