Additive manufacturing of high-strength CrMnFeCoNi high-entropy alloys-based composites with WC addition

In Situ Development and High Temperature Features of CoCrFeNi-M6Cp High Entropy-Alloy Based Hardmetal

“…Jeong et al [31] reported the Fe 41 Mn 25 Ni 24 Co 8 Cr 2 HEA (FCC) with an ultrafine grain size (≤0.5 µm) exhibited outstanding UTS (995 MPa) at room temperature but the UTS sharply dropped (less than 200 MPa) above 700 • C due to coarse grains after recrystallization. In addition, the UTS at a room temperature of FCC-based HEAs can be remarkably improved due to strengthening effects from other phases [16,18]. The forged AlCrCuNiFeCo HEA [16] with a microstructure consisting of FCC, BCC and σ phases showed a high UTS of 1170 MPa at room temperature but the UTS was very low above 700 • C (less than 100 MPa) because of the brittle to ductile transition.…”

“…Previous studies [15][16][17] indicate that the HEA of mixing of the elements in a different atomic size tend to form intermetallic phases rather than a single solid solution phase. In addition, the metal-matrix composites were reported to have better mechanical properties due to the strengthening from the particle phase [18,19]. Therefore, it is attractive to design a HEA based hardmetal consisting of a HEA matrix phase and a second strengthening phase, which may have good mechanical properties.…”

“…The CoCrFeNi HEAs possess a single FCC phase resulting in a high elongation of 60% and a relatively low ultimate tensile strength (UTS) of 453 MPa [5]. Such superior ductility of the CoCrFeNi-based HEAs makes them become a hotspot for researchers to develop particle-reinforced HEAs in order to satisfy the structural applications [6,18,19]. In previous studies, the addition of Mo induced the precipitation of σ and µ intermetallic phases [21], Nb caused the formation of Laves phase [22,23], the combination of Mo and W or W induced the formation of δ-NiW and σ-CoCr phases [15] and carbides are favorable to form in HEAs with C addition or even no C content [18,19,[24][25][26].…”

“…However, the studies on the simultaneous addition of Mo, Nb, W and C into the CoCrFeNi-based HEAs were scarcely reported. Moreover, compared to the literature on the mechanical properties of the CoCrFeNi-based HEAs at room temperature, the studies on the high temperature properties are relatively less [10,[16][17][18][27][28][29][30][31]. The high temperature properties of the FCC-based HEAs were investigated in a different status, such as as-cast [26], rolled [27,28], different grain size [10,29,30] and multiple phases [16][17][18].…”

“…Moreover, compared to the literature on the mechanical properties of the CoCrFeNi-based HEAs at room temperature, the studies on the high temperature properties are relatively less [10,[16][17][18][27][28][29][30][31]. The high temperature properties of the FCC-based HEAs were investigated in a different status, such as as-cast [26], rolled [27,28], different grain size [10,29,30] and multiple phases [16][17][18]. The ultrafine grain, rolled and multiple phases make the FCC-based HEAs possess higher room temperature mechanical properties (e.g., UTS is 995 MPa in Reference [30] and 1170 MPa in Reference [16]) but insufficient performances at elevated temperature, which the UTS is less than 600 MPa at 600 • C and basically less than 300 MPa at 800 • C. Therefore, the balance of the properties at room temperature and elevated temperature is in urgent need.…”