Stress measurement by X-Ray diffraction method for electrodeposited SnCu coating on alloy 42 substrate

A stress measurement method using SnCu coating on an Alloy 42 substrate sample, which indicated non-linear sin² Psi diagram for the coating under ordinary X-ray diffraction conditions was investigated. Diffraction profile versus 2thetas diagrams for peak indexes of (312), (501), (213), (600), (323), (541), and (631) obtained using an iso inclination method and a fixed Psi method using CuKalpha radiation showed clear peaks for some Psi angles. However, in other cases, the diagrams showed flat forms (no peaks). It was found that removing the Psi data with the flat forms from the diffraction profile versus 2thetas diagram gave a linear sin²Psi diagram for each index. Indexes with higher 2thetas degrees had a smaller confidence limit. The (631) peak with the highest 2thetas degree, which had no flat forms in the diffraction profile versus the 2thetas diagram, even with seventeen Psi data points, indicated a linear sin²thetas diagram and a confidence limit of less than plusmn2 MPa.