Effect of powder bed fusion process parameters on microstructural and mechanical properties of FeCrNi MEA: An atomistic study

TL;DR

This study uses molecular dynamics simulations to analyze how various laser powder bed fusion parameters affect the microstructure and mechanical strength of FeNiCr medium entropy alloy at the atomic level, providing insights for optimizing additive manufacturing.

Contribution

It offers the first atomistic analysis of LPBF process parameters on FeNiCr MEA, revealing how layer thickness, temperature, and laser power influence microstructure and tensile strength.

Findings

Thinner layers increase ultimate tensile strength.

Higher substrate temperature mitigates keyhole defects.

Optimal parameters balance production speed and mechanical properties.

Abstract

In our study, molecular dynamics (MD) simulations of laser powder bed fusion (LPBF) have been conducted on equimolar FeNiCr medium entropy alloy (MEA) powders. With the development of newer LPBF technologies capable of printing at the microscale, an even deeper understanding of the underlying atomistic effects of the process parameters on the microstructural and mechanical properties of the manufactured FeNiCr MEA products is required. In accordance with previous literature, the parameters of the LPBF process have been systematically varied, including layer resolution from 1 to 6, laser power from 100 {\mu}W to 220 {\mu}W, bed temperature from 300 K to 1200 K, and laser scan speed from 0.5 {\AA}/ps to 0.0625 {\AA}/ps. Consistent with prior macroscopic experimental findings, the atomistic results suggest that additive manufacturing using thinner layers imparts higher ultimate tensile strength (UTS) than fabricating with thicker layers. The latter, however, requires a shorter process time but induces keyhole defect formation if the laser-induced temperature is not sufficiently high enough. Increasing the temperature proves useful in mitigating this problem. Enhancement of UTS for the multi-rowed powders has been observed by raising the substrate temperature to 600 K or laser power to 160 {\mu}W during production. Beyond these critical limits, however, the UTS of the product diminishes due to the emergence of multiple vacancies. The results of our present study will help researchers to find a good balance between the production speed and strength of additive manufactured products at the nanoscale.