The pioneering work of Yeh (Yeh et al., 2004) and Cantor (Cantor et al., 2004) initiated an expansive research activity on high entropy alloys (HEAs), aiming at discovering novel materials in the newly opened compositional spaces. Our current interest focusses on alloys that provide pathways to dual-phase or multi-phase microstructures, thus providing more options for microstructure engineering. The alloy systems Al-Cr-Fe-Ni and Al-Co-Cr-Fe-Ni are most attractive in this respect. Both systems host compositional ranges for the design of dual-phase materials composed of face centered cubic and body centered cubic phases. The alloy design options are best explored by recurring to computational thermodynamics. A valid thermodynamic background is also required to understand the kinetic aspects of microstructure formation for a given alloy composition.  We shall present and discuss the current understanding of microstructure formation on the background of thermodynamic computations and experimental observations on solidification and solid state transformations. CALPHAD database amendments for the quaternary alloy system Al-Cr-Fe-Ni will be outlined along with application perspectives for selected alloys.