In situ alloying of AlCuSi using dual-wire-directed energy deposition with plasma

Abstract

The current research explores additive manufacturing of a multi-phase material using dual-wire plasma-directed energy deposition technology. With this approach, new materials can be designed and tested easily on the basis of commercially available consumables. In this work, AlSi5 and CuAl8 solid wire consumables are used to produce a specific AlCuSi alloy by controlling the welding parameters and the wire feed ratio. Initial experimentation results in an alloy with 85.7 at.% aluminum, 8.4 at.% copper, 2.7 at.% silicon, and 3.2 at.% magnesium, but with some instabilities during the process. The presence of magnesium in the chemical composition could be related to plasma interaction with the substrate during the welding process. After optimizing the process parameters, the chemical composition obtained is about 76.3 at.% aluminum, 19.9 at.% copper, and 3.8 at.% silicon. Using microstructural analysis via light and scanning electron microscopy, defects such as pores and inadequately melted Cu wire material are observed in all materials produced. Although the optimization of the melting process improved the microstructure, it also increased the copper content, which in turn exerts a significant influence on the mechanical properties. Mechanical testing indicates significant embrittlement. The results underscore that the microstructure is heavily influenced by the chemical composition. Microstructural changes caused by the higher copper content, i.e., in particular the increase of the volume fraction of brittle intermetallic phases such as θ-Al₂Cu, result in severe embrittlement of the obtained materials, denoted by higher hardness and reduced toughness. We conclude that the use of dual-wire plasma additive manufacturing can develop new materials by in situ alloying.