For modern aluminum alloy production, constituents of silicon, zinc, and magnesium contribute mainly to the degradation of refractory furnace linings. The alloy constituents increasingly penetrate the material via the vapor phase. This study intends to enhance understanding, describe and characterize the interactions between refractories used in holding and melting furnaces of the aluminum industry. The damage mechanisms occurring due to corrosion are verified and determined by applying various test methods and atmospheres. The present study focuses on the impact of zinc (Zn) and magnesium (Mg) as a gaseous component on refractory linings. The examined materials of this study are bauxite-based bricks with phosphate bonding and bricks with either CA 6 or sol-gel bonding, both based on high alumina. The experimental setup of the corrosion tube furnace consists of a crucible filled with solid metal and two identical bars of the refractory sample. Metallic zinc, magnesium, and the Al alloy EN-AW7075 are within this study's scope. Further conditions are a testing temperature of 1050 • C and increasing test duration of 2, 8, 24, and 36 h. The experiments have shown that zinc and magnesium both have an extreme influence, especially on the microstructure, which is accompanied by both positive and negative property changes. These are dependent on both the bonding type and the ambient atmosphere.

Corrosion is one of the most common wear mechanisms of refractories. Corrosive attacks lead to chemical and microstructural changes. Hot corrosion compromises chemical and/or physical interactions. Thus, the process is complex and not yet fully understood. Currently, corrosion is investigated post mortem by means of X-ray diffraction or scanning electron microscopy. These methods have the drawback that some information is lost on cooling. In-situ measurements, however, take measurements within the process. In resonant frequency and damping analysis (RFDA), a sample is excited to vibrate by a mechanical impulse. The vibrating sample emits an acoustic signal. This is recorded with a microphone and evaluated by means of Fast Fourier Transformation (FFT). We measured the change of the frequency of a low cement castable during the corrosion process. Further simplified experiments with less complex materials were done to confirm the results. Distinctive points of the curves could be correlated to specific corrosion phenomena, like melting or infiltration. The applied methods include a first characterization of the material with open porosity, density and in-situ high-temperature (HT)-RFDA measurements as well as a study of the slag behavior.

Refractory linings are, in addition to loads due to corrosion and creep processes, particularly affected by thermomechanical stresses caused by the restricted thermal expansion of the lining. These stresses can occur within individual components as well as in bricks and can lead to plastic deformation, cracks, and material failure. Thus, comprehensive knowledge about thermomechanical behavior is mandatory for an accurate prediction of occurring stresses to design load-optimized linings. This paper presents a method for utilizing refractoriness under load (RUL) tests to determine a temperature dependent static Young's modulus for refractories. In a first step, RUL tests with a negligible load are carried out in order to determine the materials temperature dependent thermal expansion coefficient. Afterwards, several RUL tests with higher loads are carried out. The measured data of change in temperature and length are then corrected by the thermal expansion and used to construct elastic lines for several temperatures, where the elastic slope is determined using the change in length and the respective load. Thus, Young's modulus for several temperatures can be determined. The obtained values for the Young's modulus are then compared to resonant frequency damping analysis measurements and validated using a finite element (FE) model of the RUL test.