Residual Stress Distribution of Si₃N₄/SiC Gradient Material and the Effect of Residual Stress on Material Properties

Abstract

The Si₃N₄/SiC gradient material with a gradient composition structure was prepared by a hot pressing sintering. The sinterability, distribution of residual stress and the effect of residual stress on mechanical properties of Si₃N₄/SiC gradient materials were studied. The research results show that, at 1 750 °C, Si₃N₄/SiC gradient materials with different ratios can achieve co-sintering, and the overall relative density of the sample reaches 98.5%. Interestingly, the flexural strength of Si₃N₄/SiC gradient material is related to its loading surface. The flexural strength of SiC as the loading surface is about 35% higher than that of Si₃N₄ as the loading surface. The analysis of the residual stress of the material in the gradient structure shows that the gradient stress distribution between the two phases is a vital factor affecting the mechanical properties of the material. With the increase of SiC content in the gradient direction, the fracture toughness of each layer of Si₃N₄/SiC gradient materials gradually decreases. The surface hardness of the pure SiC side is lower than that reported in other literature.

Keywords

Si₃N₄ / SiC / gradient material / residual stress / mechanical properties