SIMS imaging of Al-Li alloy welds

Secondary ion mass spectrometry (SIMS) is a powerful method for imaging microanalysis of materials. The technique involves bombardment (and consequent slow erosion) of a solid surface with an energetic ion beam, followed by mass spectrometric analysis of the ejected secondary ions to determine their quantity and sample origin. This technique enables detection of all elements and isotopes, many of them with excellent sensitivity. An added benefit is the ability to examine bulk samples polished using standard metallographic methods. When SIMS is performed in conjunction with focused ion beams, the result is surface compositional maps having high lateral resolution (35 to 100 nm). This article describes the role of SIMS in understanding the chemical phenomena associated with the formation of complex microstructures in a welded aluminum-lithium alloy. The technique is ideally suited to the study of aluminum-lithium alloys because of its extremely high sensitivity for lithium, in contrast to the virtual insensitivity of other techniques.