Functional Designing and Development of Evaluation of Residual Stress in the Surface of Inorganic Materials

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1 Evaluation of residual stress of various materialsThe range of distance in which the residual stress was observed was larger for single crystal SiC than for glass (Na-Ca-Si-O) at the primary load of 19.6N. The distance was 200μm for SiC and 300μm for glass, respectively. It was also found that the residual stress in SiC was several times larger than that in glass at an equivalent distance. The load at equivalent distance was 165MPa in SiC and 40MPa in glass, respectively.2 The change of residual stress after heat treatmentIn Si-Al-Li-O system glass, the residual stress was reduced by heat treatment and became zero near the strain point of 530℃. The residual stress curve of the crystallized glass shifted to high temperature side by about 100℃. In single crystal SiC, the residual stress started to decrease at about 800℃ and became zero at the heat treatment of 1400℃, 2hrs. The residual stress curve of polycrystalline SiC shifted a little to low temperature side.3 Analysis of materials and discussionThe reduction of residual stress by heat treatment was observed in all materials and was accompanied with three dimensional shape of the indentation. MD simulation of the diffusion of ions showed that some ions such as Ti^<4+> had intermittent movement. It is considered that the increase in heat resistance by crystallization was caused due to the suppression of viscous flow of glass owing to the crystal phase.TEM observation of single crystal SiC showed that basal slips along (0001) caused stacking faults and that the basal slip was prominent at the points close to the indentations and in the specimen which was heat treated at higher temperature. The heat resistance property which is important for semiconductor, optical and structural materials were in the order of SiC > crystallized glass > glass. The technique to evaluate residual stress can detect strain change and contribute to designing materials with high heat resistance and high functions.