High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy allo...High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy alloy and by employing advanced additive manufacturing techniques,high-performance HEACs can be fabricated.However,there is still considerable room for improvement in their performance.In this study,CoCrFeMnNi HEA powders were used as the matrix,and NiCoFeAlTi high-entropy intermetallic powders were used as the high-entropy reinforcement(HER).CoCrFeMnNi/NiCoFeAlTi HEACs were fabricated using selective laser melting technology.The study results indicate that after aging,the microstructure of HEACs with HER exhibits Al-and Ti-rich nano-oxide precipitates with an orthorhombic CMCM type structure system.After aging at 873 K for 2 h,HEACs with HER achieved excellent overall mechanical properties,with an ultimate tensile strength of 731 MPa.This is attributed to the combined and synergistic effects of precipitation strengthening,dislocation strengthening,and the high lattice distortion caused by high intragranular defects,which provide a multi-scale strengthening and hardening mechanism for the plastic deformation of HEACs with HER.This study demonstrates that aging plays a crucial role in controlling the precipitate phases in complex multi-element alloys.展开更多
The thermal decomposition kinetics of dehydroabietic acid in static state air was investigated by TG/DTA/DSC techniques with various heating rates of 5,10,15 and 20 K·min-1.TG/DTA curves showed that decomposition...The thermal decomposition kinetics of dehydroabietic acid in static state air was investigated by TG/DTA/DSC techniques with various heating rates of 5,10,15 and 20 K·min-1.TG/DTA curves showed that decomposition proceeded through a well-defined step in air.The melting point,molar enthalpy and entropy of fusion of dehydroabietic acid were determined as 445.05 K,19.74 kJ·mol-1 and 44.35 J·mol-1·K-1,by differential scanning calorimetry(DSC).The non-isothermal kinetics parameters were analyzed by means of the Kissinger and Flynn-Wall-Ozawa methods,and the thermal decomposition mechanism of dehydroabietic acid was also studied with the Satava-Sestak method.The results showed that the thermal decomposition mechanism of dehydroabietic acid in air was controlled by interface reaction R3,and the apparent activation energy and pre-exponential factor were 107.89 kJ·mol-1 and 9.33×108 s-1,respectively.展开更多
基金Project supported by ClassⅢPeak Discipline of Shanghai-Materials Science and Engineering(High-Energy Beam Intelligent Processing and Green Manufacturing),China。
文摘High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy alloy and by employing advanced additive manufacturing techniques,high-performance HEACs can be fabricated.However,there is still considerable room for improvement in their performance.In this study,CoCrFeMnNi HEA powders were used as the matrix,and NiCoFeAlTi high-entropy intermetallic powders were used as the high-entropy reinforcement(HER).CoCrFeMnNi/NiCoFeAlTi HEACs were fabricated using selective laser melting technology.The study results indicate that after aging,the microstructure of HEACs with HER exhibits Al-and Ti-rich nano-oxide precipitates with an orthorhombic CMCM type structure system.After aging at 873 K for 2 h,HEACs with HER achieved excellent overall mechanical properties,with an ultimate tensile strength of 731 MPa.This is attributed to the combined and synergistic effects of precipitation strengthening,dislocation strengthening,and the high lattice distortion caused by high intragranular defects,which provide a multi-scale strengthening and hardening mechanism for the plastic deformation of HEACs with HER.This study demonstrates that aging plays a crucial role in controlling the precipitate phases in complex multi-element alloys.
文摘The thermal decomposition kinetics of dehydroabietic acid in static state air was investigated by TG/DTA/DSC techniques with various heating rates of 5,10,15 and 20 K·min-1.TG/DTA curves showed that decomposition proceeded through a well-defined step in air.The melting point,molar enthalpy and entropy of fusion of dehydroabietic acid were determined as 445.05 K,19.74 kJ·mol-1 and 44.35 J·mol-1·K-1,by differential scanning calorimetry(DSC).The non-isothermal kinetics parameters were analyzed by means of the Kissinger and Flynn-Wall-Ozawa methods,and the thermal decomposition mechanism of dehydroabietic acid was also studied with the Satava-Sestak method.The results showed that the thermal decomposition mechanism of dehydroabietic acid in air was controlled by interface reaction R3,and the apparent activation energy and pre-exponential factor were 107.89 kJ·mol-1 and 9.33×108 s-1,respectively.
