Unveiling the phase evolution and mechanical properties of Ni1.5Co1.5CrTix alloys with ultrafine/nano structure

Abstract

Oxide dispersion strengthening (ODS) is an effective way to optimize mechanical performance, radiation tolerance and wear resistance in alloys. Therefore, in this research, lightweight and oxyphilic element Ti was utilized to induce oxides particles for in-situ fabricating ODS alloys. We investigated systematically the influence of Ti content on the phase evolution and mechanical behaviors of Ni1.5Co1.5CrTix (x = 0, 0.2, 0.4, molar ratio) multi-principal element alloys (MPEAs) fabricated by mechanically alloying and high-pressure sintering (HPS). The Ni1.5Co1.5CrTix powders presented BCC phase, FCC phase and few additional oxides. Following HPS, the BCC phase transformed to FCC phase in these MPEAs. Ni1.5Co1.5Cr MPEA was composed of FCC, Cr7C3 and Cr2O3 phases. As Ti content increased, Cr oxides or carbides gradually transformed into Ti oxides or carbides. The Ni1.5Co1.5CrTix (x = 0.2, 0.4) MPEAs after HPS displayed ultrafine grained FCC matrix and uniformly dispersed ultrafine/nano Cr-C or TiOC complex compounds. With Ti content increasing, the grain sizes of FCC matrix and precipitates had a tendency to decrease. Quantitative increment of precipitation-strengthening and fine-grain-strengthening clarifies the influence of Ti content on MPEAs. The investigations may provide key insights into tuning Ti content into the MPEAs for being available structural materials.