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Talks and Poster Presentations (with Proceedings-Entry):

E. Marks, G. Requena, H.P. Degischer, T. Buslaps, M. Di Michiel, P. Staron:
"International stresses in a short fiber reinforced Al-Si alloy during thermal cycling and after long isothermal creep";
Talk: MECA SENS IV - Conference on Stress Evaluation, Wien; 09-24-2007 - 09-26-2007; in: "MECA SENS IV - Conference on stress evaluation on materials by neutron or synchrotron radiation (Abstracts)", (2007), 45.



English abstract:
Short fiber reinforced metals (SFRMs) are directly strengthened by an effective transfer of the applied load from the matrix to the short fibers (SFs) which is increasingly effective at elevated temperatures. The ceramic reinforcement does not creep at the considered condition. In the case of Al-Si based SFRMs, the eutectic Si and the SFs form a three dimensional hybrid network. The size and shape of the Si particles interconnecting the SFs vary during high temperature and long term exposure due to the diffusion driven spheroidisation of Si. This morphological change in the hybrid network can modify the load partition between the components of the composite.
The material investigated is an AlSi12CuNiMg alloy reinforced with 15 percent in volume of random-planar oriented Saffil Al2O3 SFs, processed by squeeze casting and previously subjected to an overaging heat treatment.
The objectives of this work are:
a) to study the change of the architecture of the hybrid reinforcement during creep exposure and correlate these changes with the internal stresses acting on each component of the composite.
b) to study the evolution of residual stresses in the composite during thermal cycling.
The measurements of the residual stresses in the Si, alumina and alpha-Al after different creep exposure times are performed using neutron diffraction. In situ thermal cycling tests (between room temperature and 300 degrees Celsius with a heating and cooling rate of 3 K per minute) are carried out for the composite, and the residual stresses of the same constituents are measured using synchrotron diffraction.
The microtomographic method is applied in order to obtain the three dimensional architecture of the SFRM. Statistic techniques are used on the reconstructed volumes to extract representative volume elements (RVE) satisfying the hypothesis of ergodicity. Such RVE are used as input data for geometrical modeling and computational simulation by finite element method. The internal stresses are calculated for the thermal cycling process and for different creep exposure times and compared with the experimental measurements.

Keywords:
creep, internal stress, mmc, short fiber, thermal cycling, modeling, fem, al-si

Created from the Publication Database of the Vienna University of Technology.