A novel high entropy alloy with outstanding strength by low temperature annealing after severe cold rolling
Yukun Lv, Yuzhe Wang, Jie Zhang, Yutian Lei, Pingtao Song, Rengen Ding, Xiaofei Yao, Jian Chen
Abstract
The as-cast (Fe50Mn30Co10Cr10)97C2Mo1 HEA (high entropy alloy) was cold rolled to 90 % (CR90 %), followed by annealing at different temperatures (400 °C, 500 °C, 600 °C). Their microstructure and mechanical properties have been systematically investigated. The results show that this HEA has a single FCC structure, and that annealing at 500 °C and 600 °C leads to the formation of Cr-rich σ phase. The CR90 % HEA exhibits the tensile strength of 1926 MPa and 4 % elongation. However, annealing at 400 °C and 500 °C makes the tensile strength improve to ∼2078 MPa and ∼2060 MPa, respectively, while their plasticity does not change significantly. Annealing at 600 °C results in a significant reduction in the strength (∼1650 MPa) while a slight increase in plasticity. The element segregation and the formation of nano-sized (Fe, Mn)-rich precipitates are contributed to the significant increase in tensile strength of the HEA annealed at 400 °C. Nevertheless, annealing at 600 °C leads to a decrease in the density of defects (e.g. dislocations) caused by cold rolling and the increase in the grain size, which finally resulting in a reduction in strength.