Effect of cold rolling on microstructure and mechanical property of a novel (Fe50Mn30Co10Cr10)97C2Mo1 high entropy alloy

Abstract

Effect of cold rolling on microstructural evolution and mechanical properties of a novel (Fe50Mn30Co10Cr10)97C2Mo1 high entropy alloy has been investigated via electron microscopy and tensile testing. The results show that the alloy is mainly deformed via dislocation and twinning due to its low stacking fault energy. With increasing thickness reduction, the dislocation density first increases, up to a maximum of ∼29.3 × 1014 m−2 at CR 60 %, then reduces, to 21.1 × 1014 m−2 at CR 90 %. The width and spacing of the deformation twins gradually decrease with an increase of thickness reduction. TEM examination also reveals that shear bands produce in CR 40 % sample, and that its volume fraction gradually increases with increasing thickness reduction. Such microstructural evolution with cold rolling, gives rise to a quick enhancement of yield strength of the alloy (1926 MPa for CR 90 % vs. 239 MPa for the as-homogenized sample) whereas a clear loss in ductility. However, the cold-rolled samples at low to medium strains show a good combination of strength and ductility, e.g., CR 20 % sample has a yield strength of 800 MPa (, which is 3.3 times higher than that of as-homogenized HEA) and an elongation of 30 %, while 1300 MPa yield strength and 15 % elongation for CR 40 % sample.

Keywords

• High entropy alloy
• Cold rolling
• Deformation twin
• Shear band
• Tensile testing