HKL and X-ray Tube Selection for Diffraction-Based Residual Stress Measurement of Aluminum Materials

Aluminum is one of the most widely used structural materials due to its attractive strength-to-weight ratio, and it undergoes various heat treatments to enhance its mechanical properties and microstructure. However, thermal processes can introduce part distortion and premature failure, making precise and accurate residual stress measurement crucial for ensuring dimensional stability and extending service life. Measuring residual stress in aluminum using the X-ray diffraction technique is more complex than in other metals, such as steel or titanium, due to aluminum’s large grain size. For this reason, different crystallographic planes—such as HKL (311, 331, 333/511)—are used, although the results are not always consistent. Additionally, two different diffraction techniques, namely “sin²ψ” and “cosα,” yield varying results. The authors will present an analysis of why these measured values differ, as well as the pros and cons of each HKL selection and X-ray tube, using both diffraction techniques across different heat treatment conditions.