Effects of atom probe analysis parameters on composition measurement of precipitates in an Al-Mg-Si-Cu alloy

Abstract

Defining analysis parameter space for reliable composition measurement of materials is of significance for atom probe tomography applications. This research carefully explores the influence of specimen temperature and ultraviolet laser energy on measured compositions of precipitates and the matrix in an Al-Mg-Si-Cu alloy with atom probe tomography using voltage pulsing and laser pulsing. Low specimen temperature and high laser energy are beneficial to reduce background noise and improve mass resolution. Under both voltage pulsing and laser pulsing, the detected compositions and Mg/Si ratios of precipitates are highly sensitive to specimen temperature in the range of 20 - 80 K. In contrast, at a fixed temperature of 20 K, laser energy variation from 40 to 80 pJ provides consistent measurements in composition and Mg/Si ratio of precipitates. Related field-induced preferential evaporation and surface migration of certain elements have been discussed.