Scalmalloy and Scancromal are among new alloys which have been specifically designed for additive manufacturing processes such as Powder Bed Fusion using Laser Beam (PBF-LB). The precipitation of nanoscale Sc-rich particles plays a significant role in the microstructure and mechanical properties of these alloys. Precipitation hardening can potentially contribute to the final material strength during the built-up process, which is referred to as intrinsic heat treatment (IHT), as well during the post-heat treatment (PHT).

In this work, we develop a precipitation model based on classical nucleation and growth theories (CNGTs) [1] and adapt it to both alloys. For Scalmalloy, homogeneous precipitation of small and coherent Al3Sc phases is modeled. For Scancromal, a multi-component multi-phase approach is employed to account for mutual precipitates of types Al3Sc and Al7Cr. The model is coupled with arbitrary temperature-time data corresponding to either IHT or PHT. Temperature history during the PBF-LB process is predicted using a multi-scale thermal simulation. Different temperature profiles for various PBF-LB conditions are analysed to evaluate the impact of IHT to the precipitates number density, volume fraction and average size, as well as the resulting strength of the as-built parts. Experimental data from our own work as well as literature sources such [2–4] are used for validation of the model. The results including particle size distribution and strength are compared with common PHT conditions for the two alloys. Accordingly, IHT can be as effective as PHT, given that the inter-layer temperature sufficiently supports the nucleation and growth of particles. This can be attained primarily through active platform heating, short inter-layer times, and high energy density.