Preparation of mullite-zirconia composites from waste foundry sand and alumina

Abstract

Waste foundry sand (WFS) collected from lost foam casting (LFC) is adopted to prepare low cost mullite-zirconia composites with the addition of alumina by reaction sintering. The mixture samples of WFS and alumina as well as samples containing only WFS are sintered from 1200 to 1600°C. Thermal shock behaviors are evaluated by cool water quenching test with temperature differentials (ΔT) between 200–1000°C and 1–4 repeated cycles for ΔT = 1000°C. The degree of damage with thermal shock severity is measured through dynamic elastic modulus E using the impulse excitation method. The result shows that mullite-zirconia composites can be successfully manufactured at 1500 and 1600°C, but the thermal shock (TS) resistance for composites sintered at 1600°C is not satisfied. The critical temperature gradient (ΔT_c) is below 200°C, and after three TS cycles with ΔT = 1000°C, the E/E₀ reduced to a nearly constant.