The initial strength of the Al₂O₃ sample is relatively high at t=0, but it drops rapidly once the temperature difference approaches the critical threshold. In contrast, the initial strength of the sample with added zirconia is lower, yet the critical temperature difference increases with the amount of zirconia added. This leads to a significant reduction in the rate of thermal shock intensity loss. The thermal shock curves of both the Ze and Al₂O₃ samples are similar, but the strength of the Ze sample decreases more sharply after exceeding 200°C. Meanwhile, the strength of the Zw sample declines as the zirconia content increases, but both the critical temperature difference and the decrease in thermal shock intensity are significantly improved. For instance, the Zw15 sample maintains almost constant strength over a wide range of 0–900°C, indicating excellent thermal stability.
These experimental observations can be explained by the way zirconia particles aggregate, which is influenced by the cleaning medium used. When cleaned in water, the precipitated particles form an oxygen-linked structure during drying, leading to hard agglomeration. However, when washed in alcohol, the hydroxyl groups on the surface of hydrated zirconia gel interact through hydrogen bonding, reducing surface energy and creating steric hindrance. During sintering, the phase transformation stress between zirconia and alumina contributes to micro-crack formation, enhancing toughness but also potentially reducing strength if cracks connect and propagate.
Agglomerated zirconia helps increase crack length and resistance, raising the critical temperature difference while reducing residual strength loss. To better understand the thermal shock behavior of aluminum-zirconium materials, a multi-phase thermal shock model was developed using a functional construction method, along with universal equations, surface fitting, and isoline distribution. The strength curves of Ze-based materials show dense clustering between 100–300°C, indicating rapid strength degradation. In contrast, Zw-based materials display a ring-shaped, stepped surface, showing that the critical temperature difference increases with higher zirconia content. Once zirconia exceeds 10%, the material’s strength remains largely unaffected within 0–900°C.
By analyzing the relationship between crack propagation and temperature difference, the critical temperature difference can be theoretically calculated from crack length measurements, though this is challenging in practice. Instead, tC is estimated through data fitting and thermal shock surfaces, with crack length derived from the thermal shock damage factor Rd. Results show that Rd increases with zirconia content, and tC rises proportionally. Water washing has a greater impact on Rd, suggesting that the thermal shock damage mechanism plays a dominant role. The water-based cleaning process enhances the thermal shock performance of zirconium-aluminum refractories. At 15% zirconia content, the material retains nearly constant strength over a wide temperature range. Introducing agglomerated zirconia instead of micropores in traditional alumina effectively improves thermal shock resistance. Through the development of refractory interface models, the thermal shock behavior can be quantitatively analyzed, and the critical temperature difference can be accurately measured. The correlation between tC and Rd highlights the importance of the thermal shock damage mechanism in material performance.
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