Implementation of a strengthening model in a large-strain elasto-viscoplastic FFT-based framework for reactive additive manufactured metal matrix composites

The use of reactive additive manufacturing (RAM) techniques to produce metal matrix composite (MMC) materials provides two salient benefits. RAM-MMCs display desirable strength and mechanical performance, while the RAM process, enabled through additive manufacturing techniques such as laser powder bed fusion, produces high-quality metal parts quickly and with complex geometries. Characterization and optimization purely by physical experimentation over the entire RAM-MMC design space is cost prohibitive in terms of time and resources. Creating tailorable designs of RAM-MMCs that meet specific mechanical performance targets, thus, requires computational models that accurately capture the effects of reinforcement in RAM-MMC materials—in conjunction with the process-induced microstructure—on the hardening and damage evolution response of the material. We propose a new RAM-MMC-specific strengthening formulation, which we couple with triaxiality-based continuum damage mechanics (CDM) and implement using a large-strain elasto-viscoplastic fast Fourier transform (LS-EVPFFT) code. The new constitutive model accounts for three specific strengthening mechanisms observed in RAM-MMCs, viz., Orowan looping, grain refinement strengthening through the Hall-Petch relationship, and geometric mismatch strengthening. This framework enables simulation of deformation and failure in 3D polycrystalline RAM-MMCs, capturing the influence of varying reinforcement phase volume fractions on mechanical performance. The framework effectively captures the microstructure-to-property relationship of RAM-MMCs and opens the door to their computationally driven design.