Effect of cryotreatment on the microstructural evolution of TiAlNiCrCo and TiAlNiCrFe high entropy alloy with nano TiC precipitates

Abstract

Cryogenic treatment is imperative for improving the microstructure and mechanical properties of high-entropy alloys (HEAs). This study examines the impact of Deep Cryogenic Treatment (DCT) on the microstructural development of TiAlNiCrFe and TiAlNiCrCo HEAs produced via Mechanical Alloying (MA) and Spark Plasma Sintering (SPS). X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) investigations indicate the existence of two Body-Centered Cubic (BCC) phases, accompanied by finely scattered TiC nanoparticles. Following SPS, both alloys have a stable BCC phase, whereas DCT results in a notable decrease in crystallite size and the formation of Ni₃Ti precipitates. The mechanical characterization indicates that Vickers hardness initially rises with DCT time, peaking at 4h, after which extended exposure results in a decrease. The TiAlNiCrFe alloy demonstrates an 11.25 % increase in hardness following the ideal 4h treatment. These findings underscore the efficacy of cryogenic treatment in modifying the microstructure and mechanical properties of HEAs, providing valuable insights for sophisticated structural applications.