To overcome today’s global climate challenges the demand for lighter, stronger and more ductile, metallic materials is increasing further. One possible solution for these demands are multi-principal element alloys (MPEA). This rather young field of materials offers almost unlimited opportunities given the high number of possible chemical compositions. Nevertheless, current research in the field of single-phase face-centered cubic (fcc) MPEAs revealed, that these alloys are often characterized by a comparatively low strength. As a consequence, multi-phase MPEAs that reach superior strength levels became increasingly famous during the last years.

In the current presentation, results of the development and investigation of multi-phase MPEAs of the system Al-Co-Cr-Fe-Mn-Ni-V-C are discussed. The alloy development process was guided by a high-throughput approach that combined thermodynamic alloy screening and sample production using additive manufacturing, followed by conventional material production using casting and thermomechanical treatment. The focus is put on the additions of vanadium and carbon as well as of aluminium and carbon to single-phase MPEA base systems. Combined alloying with V and C promoted the formation of vanadium carbides, which have proven their potential for strength increase and grain refinement in AHSS. Those carbides provided a significant strength increase of up to 450 MPa, compared to a single-phase structure, while simultaneously limiting grain growth. The application of thermomechanical treatments was essential for this strength increase, but also revealed the possibility to manipulate the deformation mechanisms. Depending on the carbide fraction, the concentration of C in the fcc matrix also changed and resulted in a potential transition from TRansformation-Induced Plasticity (TRIP) to TWinning-Induced Plasticity (TWIP). Following the same methodology with additions of Al and C enabled the formation of kappa-carbides in MPEAs. The kappa phase reinforced alloys offer a great strength - ductility synergy, even in the as-printed (additively manufactured) state, reaching an ECO-index (UTS x Elongation) of 32 GPa%. Additional heat treatment increased the ECO-index to 43 GPa%.