Numerical simulation of thermal conductivity of stainless steel and Al-12Si powders for additive manufacturing

TL;DR

This paper presents a numerical model to analyze heat transfer and thermal conductivity in stainless steel and Al-12Si powders during additive manufacturing, highlighting the impact of porosity, gas environment, and particle size distribution.

Contribution

A new 3D stochastic model for simulating thermal conductivity in powder beds, accounting for gas effects and porosity-dependent heat transfer mechanisms.

Findings

Heat transfer through gas phase is significant for low-conductivity powders.

Linear models of thermal conductivity are invalid at high porosity levels.

Effective thermal conductivity depends on porosity and consolidation coefficient.

Abstract

A three-dimensional model of a partially melted powder bed with particles stochastically distributed in size and space coordinates has been developed. Numerical simulation of temperature distributions in stainless steel AISI 316L and Al-12Si powders in vacuum, air and argon has been performed to analyze unsteady heat transfer in a porous medium. The numerical model demonstrates a large effect of heat transfer through the gas phase in case of powders with low thermal conductivities like stainless steels. At the porosity level of 65\% and above, the mechanism of heat transfer drastically changes and a linear dependence of thermal conductivity on porosity frequently used in literature becomes incorrect. The effects of the consolidation coefficient and size distribution on effective heat transfer in powders are discussed. The obtained dependencies of the effective thermal conductivity on porosity and the consolidation coefficient could be used in additive manufacturing applications.