Superior resistance to high–temperature creep in an additively manufactured precipitation–hardened CrMnFeCoNi high–entropy alloy nanocomposite

Abstract

A carbon–containing CrMnFeCoNi high–entropy alloy (C–HEA) nanocomposite was additively manufactured via a laser powder bed fusion (LPBF) process combined with subsequent heat treatment. Exposure of the LPBF C–HEA to this additional heat–treatment step not only resulted in heterogeneous–structured grains of which the substructure is decorated with a dislocation network, but also uniformly distributed nanosized carbide precipitates at the grain and substructure boundaries. A multistep creep test conducted on the LPBF C–HEA at 873 K enabled the stress exponent, n, to be obtained with values of 3.03 in the low stress region (175–250 MPa) and 6.99 in the high stress region (250–325 MPa). The LPBF C–HEA alloy exhibited superior high–temperature creep resistance (i.e., the creep rate and threshold stress were minimized) compared to other CrMnFeCoNi HEAs. The mechanism underlying the creep resistance and unique creep deformation behavior of the LPBF C–HEA alloy is discussed on the basis of electron channeling contrast imaging and electron backscatter diffraction analyses.

Keywords

• Laser powder bed fusion
• High–entropy alloy matrix nanocomposite
• Carbide
• Microstructure
• Creep