Research On Residual Stress Measurement Of Sapphire Single Crystal By X Ray Diffraction

With the special crystal structure, Sapphire single crystal has excellent mechanical, optical and chemical properties, so it is widely used in military and civilian fields. However, residual stress will be introduced during in the growth processing and use process of the sapphire single crystal. Which lead to some defects, such as microcracks, dislocations,crystal boundary, resuting in the decrease of the performence. In particular,sapphire optical window usually suffer from vibration load when it works in space. In this condition, low stress brittle fracture occurs in the material, and leads to disastrous consequences. Therefore,it is of signficance to study the measurement of residual stress of sapphire single crystal.X-ray diffraction is a method of non-destruction, efficient and high precision. At present,it is the main method of residual stress measurement of single crystal materials. In the paper, the residual stress of Sapphire single crystal samples was caculated using the Pole figure maps by L-XRD. Explore and analyze the theory of multiple linear regression method for measuring residual stress of Sapphire single crystal. The correctness of the multiple linear regression method was verified by measuring residual stresses of monocrystalline silicon and iron single-crystal. The influence of the numbers of crystal face and the family of crystal planes on measuring result was analyed. Using multiple linear regression method to calculate the residual stress of the sapphire single crystal.The results showed that the principle can determine residual stress of single crystal without the effect of the reliability of stress-free lattice paramter（d₀,2θ₀）. The stress measurements of monocrystalline silicon and iron were measured by L-XRD and multiple linear regression method are consistent within the error range. Then, the theory of multiple linear regression method is correct. The residual stress of single crystal materials could be calculated by measurement of more than 4 plans.when the number of plans greater than or equal to 6, the results tended to stabilize.The σ₁₁ of the{330} crystal planes of sapphire single crystal is-241.7766MPa, the σ₁₂ is-1487.6718MPa and the σ₂₂ is-3394.2589MPa. The σ₁₁ of the{4010} crystal planes is-253.0348MPa, the σ₁₂ is-1439.0512MPa and the σ₂₂ is -3330.1074MPa.