Advances in laser assisted 3D atom probe and its applications to light metals

摘要: The three dimensional atom probe (3DAP) is the only tomography technique with an atomic resolution. Due this unique feature, it has been widely used in semi-quantitative compositional analyses of solute clusters and nanosized precipitates in alloys. Various microalloying effects in the precipitation processes of aluminum alloys have been investigated using the 3DAP. The most well-known example is the effect of trace additions of Ag and Mg in Al-Cu based alloys [1]. In this system, Ag and Mg form co-clusters in the early stage of aging, which incorporate Cu to form {111} plates. As they grow, Ag and Mg segregate to the interface between the {111} precipitate denoted as Ω and the α-Al matrix, which reduces the strain energy at the interface. From the earliest stage of the solute clustering to the coarsening stage of the Ω, the distribution of all solute atoms were visually monitored by the atom probe tomography [1]. While the combined addition of Mg and Ag leads to the formation of co-clusters, the microalloyed elements such as Sn and In are known to form fine precipitates that act as heterogeneous nucleation sites for the {001} θ ″plates [2]. Recently, the microalloying effects have also been recognized as one of the effective methods to enhance the age hardening processes in many magnesium alloys,[3]. Although magnesium alloys had not received serious attention as structural materials except in cast products, the attention towards the use of wrought magnesium alloys as the lightest structural metal for the weight reduction of automobiles and high speed trains has been increasing due to the ever increasing demand for carbon dioxide …