A hypoeutectic Al-Ni-Mg in situ composite processed by wire-arc additive manufacturing: Phase evolution and mechanical behavior

Abstract

The advent of novel processing technologies such as wire-arc additive manufacturing, distinguished by high cooling rates, requires the development of adapted feedstock materials. Here, the advantageous solidification behavior of an Al-Ni-Mg alloy was employed, whereby hot cracking can be omitted through dominant amounts of eutectic solidification. Specimens of this new alloy processed by wire-arc additive manufacturing were investigated in-depth to study the phenomena of microstructure formation and the phenomena governing the mechanical characteristics. For this purpose, the deposits were characterized using X-ray diffraction, scanning and transmission electron microscopy, differential scanning calorimetry, hardness, tensile and fracture toughness testing. Results of microstructure investigations were compared to thermodynamic calculations. The microstructure consists of α-Al/Al3Ni colonies separated by α-Al intercolony regions. Minor amounts of Al3Zr and Mg2Si second phase particles were observed. Mechanical characterization reveals ductile failure after pronounced hardening and substantial isotropic fracture toughness. The mechanical properties are discussed based on the prevalent microstructural characteristics. The presented results provide the basis for future, novel and advanced alloys dedicated for their use in wire-arc additive manufacturing.