No abstract

In the present work, a new method to predict the stress-strain curves for three-phase materials has been developed. It was applied using the example of an Mg-stabilized zirconia reinforced TRIP-matrix-composite. The content of the ceramic phase was varied between 5% and 20%, whereas the particle size of the ceramic was selected to be 30 to 50 µm. The method is a further development of mixture rule for multiphase materials with more than two microstructure components. The prediction results were compared with the original method of mixture rule and with the IsoE-method. It is shown that the new method significantly improves the convergence compared to the standard method for mixture rule, even though it does not reach the accuracy of IsoE-method. Furthermore, there is an improvement of predicted convergence for large values of the total stress. Finally, a working map was designed for a quick graphical definition of the objective functions.

A prediction model for cold flow curves was introduced for a new class of composite materials known as TRIP-matrix-composites consisting of three phases, austenite, strain-induced martensite and ZrO2. The content of the ceramic phase was varied between 0 and 30%, whereas the particle size of the ceramic was selected to be 10 to 30 μm. For the manufacturing of the composite material the powder metallurgical route including hot press procedure was chosen and very dense material could be produced.Included in the model is the hydrostatic stress σm close to the circumferential surface of the compression test sample. The hydrostatic stress was varied using different material compositions and true strain values. To calculate the cold flow curves the ISO-E-method was applied. The calculated results show a consistent congruency with the experimental data.

A metal matrix composite (MMC) consisting of AISI 304 austenitic stainless steel with up to 10 vol.‐% MgO‐PSZ was produced by a powder metallurgic process through sintering at 1300 °C and 1390 °C. The hot working of sintered samples was conducted between 900 °C and 1100 °C. The behaviour of softening kinetics was investigated using flow curve recording methods (dynamic softening) and the double‐hit method (static softening). The influence of the deformation parameters such as temperature, strain rate, inter‐pass time and relative density of the samples was determined. The microstructure development of the sintered composite after hot forming was determined by optical microscopy and SEM and was interpreted with the help of qualitative microstructure analysis. The results show a general acceleration of softening processes with increasing temperature and strain rate, with the addition of ZrO2 particles and a decrease in the density of composite materials. A mathematical‐physical model was developed to predict the softening behaviour and optimize the forming processes of the composite in the light of these results.

In the present study the resistance sintering of TRIP-Matrix-composites on the base of non-rusting austenitic steel with TRIP-effect and MgO-partial-stabilized ZrO 2 ceramic was carried out. The influence of the ceramics containing, which has been varied in the area between 5 and 20%-Vol., on the temperature development, was determined on the basis of experiments and was generalised by putting up a mathematical-physical model. The results showed a very good correspondence with the experiment. With it lets made an entire approximately description of the temperature distribution and temperature development itself during the resistance sintering of a steelceramic-composites to contribute optimum of heating rate which marks itself by a low temperature gradient about the test cross section. This methodology is able to do a useful contribution to the control of optimum sinter technology.