Study of statistical and technological size effects in cast brass

This study aims to quantify the effect of grain size and specimen volume on the static and fatigue strength of the cast brass alloy CuZn35Mn2Al1Fe1-C-GS. Specimens were extracted from a large cast component, where variations in cooling rates resulted in grain sizes ranging from about 1 mm (fine-grained) to 9 mm (coarse-grained). To evaluate the statistical size effect, tensile and uniaxial fatigue tests under pulsating tension were performed on specimens with different highly stressed volumes. Fine-grained specimens showed up to a 34% increase in fatigue strength and a 19% increase in tensile strength compared to coarse-grained ones. Similarly, smaller specimens outperformed larger ones, with fatigue strength improvements of about one-third, dependent on the microstructure. The Hall-Petch relation was used to quantify the influence of grain size, and further incorporated into a volumetric statistical size effect model. The Weibull exponent is expressed as a function of grain size and highly stressed volume, thus extending design recommendations such as the FKM-guideline towards size effects in cast brass alloys.