Development of coherent-precipitate-hardened high-entropy alloys with hierarchical NiAl/Ni2TiAl precipitates in CrMnFeCoNiAlxTiy alloys

Coherent precipitates hardening is currently emerging strengthening mechanism of the various high entropy alloys (HEAs). Recently, CrMnFeCoNiAlx HEAs have been studied to show a phase transition from face-centeredcubic (FCC) to body-centered-cubic (BCC) and formation of coherent precipitates (B2-NiAl) within the BCC matrix. The coherent precipitates in the CrMnFeCoNiAlx alloys could contribute to increase the strength but lead to considerable reduction of the ductility. The present work systematically investigated a series of CrMnFeCoNiAl0.5Tix alloys to further improve the strength and plasticity, as compared to the previously reported CrMnFeCoNiAlx HEAs. As a result, an increase of Ti addition leads to the phase transition from FCC to BCC and formation of lamellar structure and hierarchical precipitates reinforced by B2-NiAl and L21-Ni2TiAl phases. Excellent mechanical properties were achieved from CrMnFeCoNiAl0.5Ti0.1 and CrMnFeCoNiAl0.5Ti0.2 alloys. The mechanical properties of the CrMnFeCoNiAl0.5Tix alloys were discussed via theoretical strengthening mechanisms.

Automated summary

This study systematically investigated a series of CrMnFeCoNiAl0.5Tix alloys to improve strength and plasticity, resulting in a phase transition from FCC to BCC and the formation of lamellar structure and hierarchical precipitates reinforced by B2-NiAl and L21-Ni2TiAl phases. Excellent mechanical properties were achieved from CrMnFeCoNiAl0.5Ti0.1 and CrMnFeCoNiAl0.5Ti0.2 alloys, discussed through theoretical strengthening mechanisms.