Effect of reinforcement size and orientation on the thermal expansion behavior of metallic glass reinforced metal matrix composites produced by gas pressure infiltration

- First time investigation of thermal properties of metallic glass reinforced MMCs.
- Flake arrangement within the composites was analyzed by micro computed tomography.
- Layered flake arrangement leads to anisotropic thermal expansion behavior.
- Measured results were compared with several thermo-mechanical models.

Many efforts were made during the last years to utilize the superior properties of metallic glasses as reinforcements in metal matrix composites and several investigations were carried out to characterize composites' mechanical properties. Since there is a complete lack of knowledge about their thermal properties, this work focuses on the thermal expansion behavior of metallic glass reinforced metal matrix composites produced via gas pressure infiltration. The aluminum alloy AlSi12 was used as matrix material. Metallic glass Ni60Nb20Ta20 flakes with different size ranges were taken as reinforcement and volume fractions in the range of 29-44% were studied. X-ray micro computed tomography (μCT) measurements were performed to investigate the reinforcement 3D-structure within the composite. The thermal expansion behavior depending on flake orientation within the composite was investigated by dilatometric measurements. Four thermal cycles were carried out between room temperature and 500 °C at a constant heating and cooling rate of 5 °C/min. Results show that thermal strain rather depends on flake size and orientation than on volume fraction. Further, the composites exhibit a distinct anisotropic behavior for the thermal expansion coefficient (CTE) due to a layered flake structure within the composite. Finally determined CTEs were compared with several thermo-mechanical models to study the underlying mechanisms of the composite behavior.