High-entropy alloys (HEAs) are a large group of compositionally complex alloys which have invigorated research in the alloy development community in recent years. HEAs consist of multiple principle components, typically four or more, in concentrations between 5-35 at% and many HEAs have been reported to have promising thermal, structural, and irradiation-resistant properties.
Due to the vast range of possible HEA compositions, efficient exploration of the HEA composition space requires the use of high-throughput synthesis techniques. Here at UW-Madison, one of the techniques under development is in situ alloying via additive manufacturing. This is performed using an Optomec LENS MR-7, as schematic of which is shown in Figure 1. Here, four powder hoppers are each filled with a single elemental powder which can be drawn into the system at different feed rates using independently controlled augers. The desired ratio of elemental powders is transported to the print head using pressurized argon which mixes the powders in flight. The mixed powder exits the print head through four nozzles which direct the powder into the path of a 1-kW continuous-beam laser. At the intersection of the laser and powder, a pool of molten metal forms – by translating the build plate, the melt pool can be moved across the build plate leaving solidified material in its wake.
This technique allows for a desired alloy composition to be produced in bulk quantities rapidly. Additionally, since the composition of the incoming powder can be changed on the fly, graded materials and sample arrays of different compositions can be produced. Such sample arrays can then be heat treated, mechanically tested, irradiated, and characterized in a high-throughput fashion which greatly increases the speed of materials screening and supports the investigation of HEAs for nuclear applications. As part of this work, the following elemental powders are being used for alloy development and screening: Cr, Fe, Mo, Mn, Nb, Ni, Ta, Ti, V, and W.