Influence of Ti on the temperature-dependent strength-ductility behavior of Al_0.25CrFeNiTi high-entropy alloys prepared by MA-SPS

The Al_0.25CrFeNiTi_x(x = 0.15, 0.25, 0.35, 0.45)high-entropy alloys (HEAs) were fabricated via mechanical alloying followed by spark plasma sintering (MA–SPS). The Ti content significantly controls the microstructure and temperature-dependent mechanical properties. During ball milling, Ti governs the competition between cold welding and fracture, affecting powder size and the dominant BCC phase formation. After sintering, the alloys retained a dual-phase FCC/BCC structure. As Ti content increased, ordered AlNi₂Ti and B2 phases precipitated, and further elevation to x = 0.45 led to the formation of brittle σ and Ni₃Ti phases formed. Ti content was found to be a critical regulator of mechanical properties. The Ti_0.25 alloy exhibits optimal room-temperature performance (σ_0.2 = 2070.95 MPa, ε_p = 15.80%), whereas the Ti_0.35 alloy demonstrates excellent high-temperature strength at 650 °C (σ_0.2 = 997.32 MPa). The distinct performance at different temperatures is closely related to the Ti-induced microstructural features. Quantitative strengthening analysis further indicates that the high room-temperature yield strength of Ti_0.25 alloy arises mainly from solid solution strengthening (936.45 MPa) and grain refinement strengthening (590.40 MPa). This work clarifies the microstructure evolution driven by Ti addition in Al_0.25CrFeNiTi HEAs. These findings provide a theoretical foundation for the design and optimization of non-refractory HEAs for medium and high temperature structural applications.