Session: 01-03 -01: Advanced Manufacturing and Process–Structure Relationships in Aerospace Structures

Paper Number: 190371

190371 - Towards Microstructure Control in Laser Powder Bed Fusion of Inconel 718 Alloys 

Microstructure evolution in Laser Powder Bed Fusion (LPBF) is controlled by thermal histories that vary with process parameters, scan strategy, and geometry‑dependent heat accumulation. The widely used single‑track process maps are insufficient to capture these multi‑track interactions, limiting their ability to predict melt‑pool behavior and resulting microstructural features at part scale.

This study introduces a microstructure‑aware, multi‑dimensional process‑mapping framework that integrates multi‑track thermal FE simulations using Ansys Mechanical and surrogate modeling to quantify how scanning strategy, hatch spacing, and pre‑deposition temperature influence melt‑pool geometry and cooling‑rate fields in Inconel 718.

The results reveal substantial shifts in the acceptable process window driven by scan‑strategy‑dependent heat buildup, with cooling rates varying by almost an order of magnitude under otherwise identical power–speed conditions. Experimental validation using NIST AM‑Bench thermography shows good agreement with the predicted cooling rates. In addition, stepped‑pyramid parts confirm predicted correlations between cooling rates and cellular microstructure, including trends toward columnar-to-equiaxed transition driven by thermal gradients and cooling-rate variations.

Leveraging the surrogate model's predictive capability, adaptive optimization of laser power and hatch spacing is demonstrated to achieve target cooling‑rate regimes while avoiding porosity. The proposed framework establishes a pathway for microstructure control in LPBF and enables geometry‑aware, scan‑strategy‑informed process optimization for LPBF-manufactured components.

Presenting Author: Ali Najafi Synopsys

Presenting Author Biography: Ali Najafi holds a PhD in computational engineering focused on structural mechanics simulation and ICME. He leads a customer-facing engineering team and is responsible for technical strategy, execution, and people development across multidisciplinary topics (solvers, materials modeling, calibration/testing, and workflow automation).