Band 57, Heft 9

The mechanical properties of the particulate reinforced composites are profoundly affected by two significant factors, fraction of reinforcement in the matrix and the distribution of the reinforced particles in the matrix. In this paper, a novel approach is adopted where a newly developed distribution index and area fraction of the composites are quantitatively determined through microstructural image analysis method, and the process parameters are optimised for maximum area fraction and minimum distribution index. The distribution index ( D index ) is calculated by estimating the free-path spacing within particles. The stir casting process parameters (stirrer rpm, time of stirring, furnace temperature and preheat temperatures) are optimised by Box-Behnken design of response surface methodology. The quantitatively assessed responses provide an authentic base for optimisation of process parameters. The experimental responses corresponding to the optimised parameters are within the range of the responses estimated by the confirmation test of optimisation with a 95 % confidence level.

The subject of this paper is the use of conventional and advanced metallographic techniques for the development and characterization of high-performance materials. It provides the author's personal retrospective, spanning the years from 1980 until the present day and ranging from functional to structural materials. The metallographic techniques discussed in this article include light optical as well as scanning electron microscopy, conventional and high-resolution transmission electron microscopy, microprobe and atom probe tomography. Furthermore, additional and complementary procedures such synchrotron radiation and neutrons will be outlined.

Fractured wire ropes of a pantograph actuator system for electrical trucks were received from the client. They failed by low cycle fatigue (LCF) fracture during service in a customized test rig. The client reported wide scatter of the number of testing cycles to failure. A laboratory order was placed for a metallurgical failure analysis of the subject stranded ropes, this to derive recommendations for design improvements, so that the minimum number of cycles to failure could be increased, and the scatter decreased.