The CoCrFeNiMn high entropy alloy was produced by homogenization, cold rolling and recrystallization. The effects of thermomechanical processing on microstructures and tensile properties at different temperatures were...The CoCrFeNiMn high entropy alloy was produced by homogenization, cold rolling and recrystallization. The effects of thermomechanical processing on microstructures and tensile properties at different temperatures were investigated using X-ray diffractometry（XRD）, optical microscopy（OM）, scanning electron microscopy（SEM） and multi-functional testing machine. The results show that dendritic structures in cast alloy evolve into equiaxed grains after being recrystallized, with single face-centered cubic（FCC） phase detected. The most refined alloys, stemming from the highest rolling ratio（40%）, exhibit the highest strength due to the grain boundary strengthening, while the variation of elongation with temperature shows a concave feature. For the coarse-grained alloys, both the ductility and work hardening ability decrease monotonically with increasing temperature. Serrated flow observed at intermediate temperatures is attributed to the effective pinning of dislocations, which manifests the occurrence of dynamic strain hardening and results in the deterioration in ductility. Besides, dimples on the fracture surfaces indicate the typical ductile rupture mode.展开更多
Microstructures and mechanical properties of dual-phase AlxCrMnFeCoNi (x=0.4, 0.5, 0.6, at.%) alloys were investigated. Thermomechanical processing leads to a microstructural evolution from cast dendritic structures t...Microstructures and mechanical properties of dual-phase AlxCrMnFeCoNi (x=0.4, 0.5, 0.6, at.%) alloys were investigated. Thermomechanical processing leads to a microstructural evolution from cast dendritic structures to equiaxed ones, consisting of face-centered cubic (fcc) and body-centered cubic (bcc) phases in the two states. The volume fraction of bcc phase increases and the size of fcc grain decreases with increasing Al content, resulting in remarkably improved tensile strength. Specifically, the serrated flow occurring at the medium temperatures varies from type A+B to B+C or C as the testing temperature increases. The average serration amplitude of these Al-containing alloys is larger than that of CoCrFeNiMn alloy due to the enhanced pinning effect. The early small strain produces low-density of dislocation arrays and bowed dislocations in fcc grains while the dislocation climb and shearing mechanism dominate inside bcc grains. The cross-slip and kinks of dislocations are frequently observed and high-density-tangled dislocations lead to dislocation cells after plastic deformation with a high strain.展开更多
基金Project(11572306)supported by the National Natural Science Foundation of China
文摘The CoCrFeNiMn high entropy alloy was produced by homogenization, cold rolling and recrystallization. The effects of thermomechanical processing on microstructures and tensile properties at different temperatures were investigated using X-ray diffractometry（XRD）, optical microscopy（OM）, scanning electron microscopy（SEM） and multi-functional testing machine. The results show that dendritic structures in cast alloy evolve into equiaxed grains after being recrystallized, with single face-centered cubic（FCC） phase detected. The most refined alloys, stemming from the highest rolling ratio（40%）, exhibit the highest strength due to the grain boundary strengthening, while the variation of elongation with temperature shows a concave feature. For the coarse-grained alloys, both the ductility and work hardening ability decrease monotonically with increasing temperature. Serrated flow observed at intermediate temperatures is attributed to the effective pinning of dislocations, which manifests the occurrence of dynamic strain hardening and results in the deterioration in ductility. Besides, dimples on the fracture surfaces indicate the typical ductile rupture mode.
基金Project(11572306)supported by the National Natural Science Foundation of ChinaProject(WK2090050040)supported by the Fundamental Research Funds for Central Universities,China
文摘Microstructures and mechanical properties of dual-phase AlxCrMnFeCoNi (x=0.4, 0.5, 0.6, at.%) alloys were investigated. Thermomechanical processing leads to a microstructural evolution from cast dendritic structures to equiaxed ones, consisting of face-centered cubic (fcc) and body-centered cubic (bcc) phases in the two states. The volume fraction of bcc phase increases and the size of fcc grain decreases with increasing Al content, resulting in remarkably improved tensile strength. Specifically, the serrated flow occurring at the medium temperatures varies from type A+B to B+C or C as the testing temperature increases. The average serration amplitude of these Al-containing alloys is larger than that of CoCrFeNiMn alloy due to the enhanced pinning effect. The early small strain produces low-density of dislocation arrays and bowed dislocations in fcc grains while the dislocation climb and shearing mechanism dominate inside bcc grains. The cross-slip and kinks of dislocations are frequently observed and high-density-tangled dislocations lead to dislocation cells after plastic deformation with a high strain.
