In this paper we present the theoretical background of the New Rheocasting (NRC) process, which is based on the thixotropic behavior of a melt with a globulitic primary phase. The NRC process ...represents an economic alternative to the forging process. The main goal of this study was an evaluation fo the microstructure of this innovative and ecologial production process. We present some characteristic microstructures observed during the evaluation of a slurry and a real automotive component. Some dendritic forms of the primary alphaAl phase were observed in the component, which means there are possibilities for a further improvement of the temperature regime. An increased content of the eutectic phase near the surface was observed and inclusions with strontium were found in the eutectic phase.
Based on experimental data and transmission electron micrographs an explanation of the mechanism of the change of Charpy notch transition temperature after strain ageing is proposed. The explanation ...involves the interplane ordering of carbon atoms at ageing annealing at 250 deg C as a synergy of the dislocation structure and the redistribution of carbon atoms in solid solution in ferrite. The induced internal stresses decrease the cleavage fracture strength of the ferrite matrix and increase the Charpy notch toughness transition temperature.
A comparison of performance of AlTi5B1 and AlTi3C0.15 grain refiners in commercial-purity aluminum AA 1080 at contents up to 10 g*kg-1 for AlTi5B1 and 16 g*kg-1 for AlTi3C0.15 grain refiner is ...studied in this work. The results show that AlTi5B1 grain refiner is much more effective in suppressing the growth of columnar grains at the same titanium content. AlTi5B1 grain refiner in comparison to AlTi3C0.15 grain refiner also shows smaller grain size at the same titanium content except at the highest one. It was observed that the effectiveness of AlTi5B1 grain refiner decreases at the content above 4 g kg-1. Similar behaviour was not found for AlTi3C0.15 grain refiner. The differences in the behaviour of the both refiners at the high refiner content can be explained by the differences in the mechanism of the grain refinement.
Inclusions in primary aluminium were analysed with an electron-probe microanalyser and a high-resolution Auger electron spectrometer. In multiphase eutectic and complex inclusions the presence of ...calcium, magnesium, iron, copper, molybdenum and aluminium was detected. Prior to Auger analysis, sufficient ion etching is necessary for the elimination of oxides from the surface. The complex inclusions, with calcium content, reacted with water which demanded the choice of a suitable technique for the preparation of metallographic samples.
