Abstract
As a classic high-entropy alloy system, CoCrFeNiMn is widely investigated. In the present work, we used ZrH2 powders and atomized CoCrFeNiMn powders as raw materials to prepare CoCrFeNiMnZrx (x = 0, 0.2, 0.5, 0.8, 1.0) alloys by mechanical alloying (MA), followed by spark plasma sintering (SPS). During the MA process, a small amount of Zr (x ≤ 0.5) can be completely dissolved into CoCrFeNiMn matrix, when the Zr content is above 0.5, the ZrH2 is excessive. After SPS, CoCrFeNiMn alloy is still as single face-centered cubic (FCC) solid solution, and CoCrFeNiMnZrx (x ≥ 0.2) alloys have two distinct microstructural domains, one is a single FCC phase without Zr, the other is a Zr-rich microstructure composed of FCC phase, B2 phase, Zr2Ni7, and σ phase. The multi-phase microstructures can be attributed to the large lattice strain and negative enthalpy of mixing, caused by the addition of Zr. It is worth noting that two types of nanoprecipitates (body-centered cubic (BCC) phase and Zr2Ni7) are precipitated in the Zr-rich region. These can significantly increase the yield strength of the alloys.
Highlights
During the past few years, high-entropy alloys (HEAs), a type of multi-principal-element alloy, have drawn widespread attention form worldwide material scientists [1,2,3]
We focused on the novel high-entropy alloy system of CoCrFeNiMnZrx (x = 0, 0.2, 0.5, 0.8, 1.0)
The main conclusions of the present work are given below: (1) Metastable single face-centered cubic (FCC) phase CoCrFeNiMnZrx alloy powders were prepared after 30 h of ball milling, which means that mechanical alloying (MA) could enhance the solid solubility of large size elements in the matrix
Summary
During the past few years, high-entropy alloys (HEAs), a type of multi-principal-element alloy, have drawn widespread attention form worldwide material scientists [1,2,3]. The preparation of HEAs powders by gas atomization is a rapid solidification process [18], in which grain growth and element segregation are inhibited, and the high cooling rate even leads to the formation of an amorphous phase [14]. It is feasible to change the phase composition and improve the mechanical properties of AlCoCrFeNi by adding an alloying element. The large atomic size difference and negative enthalpies of mixing [24] between Zr and other constituent elements can produce a strong lattice distortion and even change the phase composition, which may improve the mechanical properties of the CoCrFeMnNi. In this paper, we focused on the novel high-entropy alloy system of CoCrFeNiMnZrx (x = 0, 0.2, 0.5, 0.8, 1.0). The alloying behavior, microstructures, and mechanical properties of both powders and sintered alloys were investigated
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