The hypo-eutectic medium entropy alloy Al0.75CrFeNi2.1 was designed for additive manufacturing, specifically laser powder bed fusion (LPBF). The off-eutectic composition allows obtaining an FCC-rich microstructure during the fast and directional solidification in the melt pool. Its solidification pattern is mainly cellular with an average cell spacing of about 0.5 µm (Figure 1). The spinodally decomposed BCC phase forms as a thin envelope around the primary FCC cells. During post-build annealing an ultrafine quasi-lamellar pattern emerges, following BCC growth and coarsening [1]. The pronounced anisotropy of the FCC / (B2)BCC phase boundary energy drives the observed lamellar alignement.

The mechanical properties of the alloy depend on the post-build annealing conditions and exceed by far the strength of the as cast eutectic reference alloys Al0.8CrFeNi2.1 and AlCoCrFeNi2.1, respectively. The properties are comparable to hot rolled AlCoCrFeNi2.1 [1, 2].

We will present and discuss (i) the criteria for alloy selection, (ii) the selection of LPBF parameters, (iii) the microstructure’s response to subsequent annealing treatments and (iv) an overview of mechanical properties as function of the applied annealing conditions and related microstructural features.