We present a brief review of the microstructures and mechanical properties of selected metallic alloys processed by additive manufacturing (AM). Three different alloys, covering a large range of technology readiness levels, are selected to illustrate particular microstructural features developed by AM and clarify the engineering paradigm relating process–microstructure–property. With Ti-6Al-4V the emphasis is placed on the formation of metallurgical defects and microstructures induced by AM and their role on mechanical properties. The effects of the large in-built dislocation density, surface roughness and build atmosphere on mechanical and damage properties are discussed using steels. The impact of rapid solidification inherent to AM on phase selection is highlighted for high-entropy alloys. Using property maps, published mechanical properties of additive manufactured alloys are graphically summarized and compared to conventionally processed counterparts.
Using both experimental and modeling approaches, we give some clarifications regarding the mechanisms of interaction between ferrite recrystallization and austenite formation in cold-rolled high-strength steels. Using different thermal paths, we show that ferrite recrystallization and austenite formation can be strongly interdependent. The nature of the interaction (weak or strong) affects significantly the austenite formation and the resulting microstructure. We show that the kinetics of austenite formation depends intrinsically on both heating rates and the extent of ferrite recrystallization. An unexpected behavior of austenite growth was also seen at high heating rates. A possible explanation is presented based on the nature of the local equilibrium at the ferrite-austenite interface. The microstructure is more heterogeneous and anisotropic when both austenite formation and ferrite recrystallization overlap. A mechanism of microstructural formation is proposed, and this is supported by 2D simulations' images.
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