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On novel Ni-rich phase formed during aging of an additively manufactured ultra-high strength CoFeNi alloy
Mengchao Zhang a , Qiuyue Wu a , Qingdong Liu b,* , Zemin Wangc , Hui Li a,*
aschool of Materials Science and Engineering, Shanghai University, Shanghai 200444, PR China
bSchool of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China
cSchool of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418, PR China
Abstract:
The precipitation mechanism of strengthening phase of a body-centered-cubic (BCC) structured CoFeNi multi- principal element alloy produced by additive manufacturing was studied by transmission electron microscopy (TEM) and atom probe tomography (APT). The hardness of CoFeNi alloy achieved the peak value of 554.79 ± 9.86 HV after aging for 160 h at 400 ◦ C. The CoFeNi alloy exhibited an ultrahigh compressive yield strength and ultimate compressive strength up to 1.8 GPa and 2.3 GPa respectively, whilst maintains a strain of 18.9 %. The microstructure of the alloy exhibited nanoscale lamellar Ni-rich phase with high stability homogeneously distributed in BCC matrix after aging at 400 ◦ C. The novel Ni-rich phase containing about 50 at. % Ni with a hexagonal structure is the mainly precipitation strengthening phase, and has coherent orientation relationship with the BCC matrix in the< 101 > bcc ‖< 1120 > Ni and {111}bcc ‖ {0001}Ni. Based on the experimental re sults, the precipitation mechanisms of the Ni-rich phase were discussed in detail. The current work provides a possible new direction to design high-strength alloy by introducing the novel Ni-rich phase.
On novel Ni-rich phase formed during aging of an additively manufactured ultra-high strength CoFeNi alloy.pdf
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