Microstructure and properties of (Fe35Ni35Cr20Mn10)95.3Ti4.7 high-entropy alloys regulated by homogenizing treatment

Abstract

The influence of homogenizing treatment on the microstructural evolution and mechanical behavior of the (Fe35Ni35Cr20Mn10)_95.3Ti_4.7 high-entropy alloy (HEA) was systematically investigated. Microstructural characterization was conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), while mechanical properties were evaluated via tensile testing using a CMT5105 machine. Experimental findings revealed that as the homogenization temperature increased from 800 °C to 900 °C, the η-Ni₃Ti phase evolved from grain-boundary precipitation to intragranular dispersion, adopting fine sheet-like or rod-like morphologies. At 1000 °C for 12 h, the intragranular η-Ni₃Ti phases dissolved into the matrix, leaving only grain-boundary precipitates. Further elevating the temperature to 1100 °C resulted in complete dissolution of the grain-boundary η-Ni₃Ti phases into the matrix, forming a single-phase structure. Correspondingly, the prepared HEAs exhibited a progressive decline in strength but a marked enhancement in plasticity, with the fracture mode transitioning from brittle to ductile. Prolonged homogenization at 1000 °C led to a gradual reduction in grain-boundary η-Ni₃Ti phases with increasing treatment duration, concomitantly improving both strength and plasticity. Optimal comprehensive mechanical properties were achieved after 15 h of treatment at 1000 °C. The increase in yield strength is attributed to η-Ni₃Ti phases pinning of dislocations and dislocations proliferation during deformation. Enhanced ductility results from coordinated deformation between the η-Ni₃Ti phase and matrix, driven by dislocation cell formation. These cells alleviate local stress concentrations, while coherent interfaces enable limited dislocation transfer across phase boundaries, delaying necking and fostering work hardening.