Compositional gradient affects the residual stress distribution in Si3N4/SiC functionally graded materials

Residual stress greatly affects the mechanic performance of the functionally graded materials (FGM). The residual stress distributions in different Si 3 N 4 /SiC FGMs formed in the fabricating processes were investigated with X-ray diffraction method in this work. It's found that residual stresses in FGMs with different component gradients were the gradient function of the quadratic of the component content and mainly determined by gradual changes of thermal mismatch and elastic modulus caused by the component content gradient. And the maximum tensile strength of FGM was limited by the ultimate tensile strength or shearing strength of SiC . When the maximum tensile strength exceeded the ultimate tensile strength or shearing strength of SiC and the maximum residual stress was maintained within the ultimate limit and resulted in the newly balanced stress distribution due to the same gradient function, cracks were formed. These results obviously provide ideas for regulating the performance and designing the FGM gradient for some special applications.