Influence of Ti Addition on Microstructural Evolution, Mechanical Properties, and Corrosion Resistance in Al_0.6CrFeNi_2.4 Multi-principal Element Alloys

Given the well-established role of Ti as both a reinforcing and passivating element, we designed a series of multi-principal element alloys (MPEAs) based on the ductile and corrosion-resistant Al_0.6CrFeNi_2.4 alloy. These alloys, denoted as Al_0.6CrFeNi_2.4Ti_x (x = 0, 0.2, 0.4, 0.5, and 0.6), aimed at achieving optimal synergy in mechanical properties and corrosion resistance. As Ti content increased from x = 0–0.5, a notable transition from columnar to equiaxed microstructures was observed, with the primary dendrite arm spacing decreasing from 17.2 μm to 8.3 μm, attributed to the Ti-induced constitutional supercooling. These structural changes played a vital role in improving yield strength, increasing from 376 MPa to an impressive 2074 MPa. Moreover, the Ti dissolution in the (Cr, Fe)-rich FCC phase facilitated the formation of more protective and densely packed passive films, resulting in a comprehensively outstanding performance of the Al_0.6CrFeNi_2.4Ti_0.2 (i.e., self-corrosion voltage/current of − 0.159 V and 2.6 × 10⁻⁷ A/cm² together with a plastic strain of 35.8% and an impressive high fracture strength of 2811 MPa). This research demonstrates the potential of tailored Ti alloying to enhance the comprehensive properties of MPEAs, offering exciting possibilities for advanced materials in various engineering applications.