In contrast, under quasi-static tension, only dislocation slip dominates, accompanied by dislocation entanglement and massive pile-ups. Besides, short range order may seriously hinder the dislocation movement, especially when the thermal activation of dislocations gradually fails at high strain rates, which limit the dislocation slip to a smaller scale and result in deformed sub-grains. Deformation-induced twinning further improves the strain-hardening ability of the alloy. Upon dynamic tension, the simultaneous enhancements of both strength and ductility are attributed to the joint activation of multiple strengthening mechanisms. The strain rate sensitivity under quasi-static tension is 0.0172, in contrast to 0.3978 under dynamic deformation. Meanwhile, the elongation is slightly improved as the strain rate rises.
The yield strength and ultimate tensile strength are increased from 398 MPa to 679 MPa at 10 −4 s −1 to 743 MPa and 1412 MPa at 3000 s −1, respectively. A heterogeneous structure composed of a phase distribution and grain size is formed.
This alloy consists of a tetragonal σ phase and minority M 23C 6 carbides embedded in the continuous FCC matrix after thermomechanical treatments. Face-centered-cubic (FCC) Fe 40Mn 20Cr 20Ni 20 high-entropy alloys (HEAs) with a weigh of 50 Kg were fabricated by industrialized vacuum-induction melting.