Effect of Ti on Characterization and Properties of CoCrFeNiTix High Entropy Alloy Prepared Via Electro-Deoxidization of the Metal Oxides and Vacuum Hot Pressing Sintering Process

Abstract

The CoCrFeNi system is one of the most important high entropy alloys (HEAs) systems. By adding and adjusting the alloy element components and using different synthesis methods, different phases, organization and microstructure can be obtained, thus improving their properties. In this study, CoCrFeNiTix HEAs with various Ti contents (x in molar ratio, x = 0, 0.5, 1.0, 1.5) were fabricated by an electrochemical process by virtue of different oxides. The impacts of different Ti contents on the structure, distribution of elements, mechanical properties and corrosion behavior were researched using XRD, EDX and other testing methods. The bulk CoCrFeNiTix (x = 0, 0.5, 1.0, 1.5) HEAs could be obtained through vacuum hot pressing sintering process (VHPS), which had a single-phase FCC structure. The results of the study showed that the bulk CoCrFeNiTix exhibited superior ultimate tensile strength (UTS) and hardness, with the UTS of CoCrFeNiTi as high as 783 MPa and the hardness of CoCrFeNiTi1.5 reaching 669 HV. The corrosion behavior of CoCrFeNiTix (x = 0, 0.5, 1.0, 1.5) HEAs in 0.5 M H2SO4, 1 M KOH and 3.5 wt% NaCl was improved with addition of Ti. CoCrFeNiTix (x = 0, 0.5, 1.0, 1.5) HEAs have great potential for application in the fields of biomedical coating and aerospace, as well as extreme military industry, etc.

Influence of Tooling on the Properties of the Surface Layer in HEA Alloy Sinters Produced by the SPS Method

“…Nowadays, a commonly used technique is arc melting, although it is usually followed by homogenization at a high temperature. Promising results have been achieved when powder metallurgy methods have been applied, e.g., hot pressing sintering [14][15][16]. However several experiments using Spark Plasma Sintering have been proposed, with exceptional results being achieved in terms of grain size and strength.…”

Effect of Annealing Temperature on the Microstructure and Mechanical Properties of CoCrFeNiNb0.2Mo0.2 High Entropy Alloy

“…However, the relatively low strength at room temperature limits their application prospects. To address this issue, a variety of strengthening mechanisms have been adopted, including grain refinement [12,13] and precipitation strengthening [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

“…However, it may also cause a decrease in ductility. When CoCrFeNi is alloyed with Ti [28,30], the resulting material undergoes a phase evolution. Specifically, as the molar content of Ti increases from 0 to 0.5, there is a transformation in the phase formation from FCC to FCC + σ + R and eventually to FCC + Laves + σ + R. The addition of Ti to FCC HEAs resulted in an increase in compressive strength from 871 MPa to 1502 MPa.…”