Abstract
Thermal and structural properties of fused and crystalline quartz were studied for use in ceramic shells during the casting of Fe-Mn-Co-Ni-Cr-Nb-Mo quasi-high-entropy alloys (QHEAs). The phase composition was determined by X-ray phase analysis, while thermal expansion was measured using the dilatometric method. Fused quartz exhibits an amorphous mono-phase structure, high phase and chemical purity, and a low coefficient of linear thermal expansion, which ensures dimensional stability and enhances the thermal resistance of ceramic shells during heating. Crystalline quartz, in contrast, undergoes polymorphic transformations, experiences abrupt expansion, and develops internal stresses, increasing the risk of microcrack formation. Comparative analysis confirms the superiority of fused quartz for investment casting technologies, reducing defect formation and improving the reliability of ceramic shells in the production of QHEA castings