Page 16 - Read Online

Page 10 of 21 Zhou et al. J Mater Inf 2022;2:18 https://dx.doi.org/10.20517/jmi.2022.27

Figure 9. (A) Tensile stress-strain curve of as-printed CoCrFeMnNi HEA in different atmospheres with work hardening rate curve
inserted. (B) Schematic diagram showing the in situ doping of nitrogen through the L-PBF process under a reactive N atmosphere and
[92] 2
the inset showing the annular bright-field STEM image of N-50 HEA .

[83]
Figure 10. Microstructure and tensile properties of ODS HEA by L-PBF and schematic diagram showing oxide formation mechanism .
ODS: oxide-dispersion-strengthened; HEA: high-entropy alloys.
[96,97]
resistance of the FeCoCrNiMn HEA fabricated by L-PBF .

An incoherent interface is prone to cause stress concentration during deformation. Thus, the contents of the
incoherent precipitations are usually controlled to a low level, which in turn limits their strengthening
effects on the matrix. As discussed above, the L1 precipitation coherent with the FCC HEA matrix can
2
maintain a high content, significantly improving the tensile strength without sacrificing ductility. Mu et al.
broke the strength-ductility trade-off by introducing high-density dislocation networks and disordered L1
2
precipitates to the FCC HEA matrix (Fe Co Ni Al Ti , at. %) through the L-PBF and the subsequent
[89] 28 29.5 27.5 8.5 6.5
heat treatment . Compared with the conventional L1 -strengthened HEA, the pre-existing high-density
2
dislocation networks of the as-printed sample provided a fast diffusion channel for the solute atoms.
Therefore, the L1 precipitation was preferentially formed near the high-density dislocation networks during
2
the aging process. Thus, an ultrahigh strength of ~1.8 GPa and a maximum elongation of ~16% were
achieved for the as-printed FeCoNiAlTi HEA after aging at 780 °C for 4 h [Figure 11A]. The large ductility
mainly came from the evolution of multiple stacking faults (SFs) [Figure 11B], while the ultrahigh strength
was mainly derived from dislocation-precipitation synergistic strengthening [Figure 11C and D]. This work
provided an efficient method to develop high-performance HEAs by simultaneously introducing