Al-alloys have a higher strength compared to pure aluminum. This is why the Al-alloys are used in many areas of light weight construction. In the project presented here, Al-Si casting alloys are examined, for example, for use in cylinder heads and crankcases.
Type 2 Residual Stress
Since the aluminum and silicon have different coefficients of thermal expansion as the molten mass solidifies during cooling, besides the usual macroscopic residual stress, additional residual stress develops at the microscopic level, the so called type 2 residual stress. These residual stresses, which previously could not be measured, represent high material strain on microscopically small areas and play a major role in crack formation in the castings.
Together with project partners these type 2 residual stresses were measured by means of neutron diffraction separately in each phase of the Al-Si structure and are taken into account, for the first time, in the microstructure simulation developed at ITWM, which enables mechanical properties such as stiffness, plastic flow, and strength to be predicted much more accurately than before. These results can be used to calculate the fatigue of the component.