Understanding Microstructure Evolution During Additive Manufacturing of Metallic Alloys Using Phase-Field Modeling

Additive manufacturing of metallic alloys involves non-uniform temperature distributions and rapid thermal cycles that result in microstructures featured with anisotropy, which differ drastically from their cast or wrought counterparts. Such different microstructure features critically affect the mechanical properties of the AM builds. In this chapter, we briefly review the existing experimental and simulation studies on the microstructure aspects during AM of metallic alloys, especially Ti-6Al-4V. A multi-scale computational framework is proposed to understand the microstructure evolution process during AM and applied to Ti-6Al-4V alloys: (i) macroscopic finite element calculations for temperature distribution and thermal history; (ii) grain-scale phase-field model for solidification and grain growth; (iii) sub-grain-scale phase-field model for β→α phase transformations. We demonstrate the proposed framework by simulating the microstructure evolution during selective electron beam melting (SEBM) of a Ti-6Al-4V component in terms of both β-grain textures and (α+β) microstructure features.