A series of Alx(CoCrNi)100-x(x=0-21 at.%)medium-entropy alloys(MEAs)were designed and prepared to investigate the effects of Al addition on the microstructures and tensile properties.The results reveal that the lattic...A series of Alx(CoCrNi)100-x(x=0-21 at.%)medium-entropy alloys(MEAs)were designed and prepared to investigate the effects of Al addition on the microstructures and tensile properties.The results reveal that the lattice structure changes from the initial single FCC structure(x<10 at.%),to the FCC and disordered BCC structures(x=10 and 11 at.%),then to the FCC and BCC/B2 structures(11<x<21 at.%),finally to the duplex BCC/B2 structures(x≥21 at.%)with increasing Al addition.Consistent with microstructures,significant changes also occur in the corresponding tensile properties with Al addition,showing that the strength increases and the ductility decreases with increasing Al addition.Especially,the Al-15 MEA exhibits an acceptable balance of strength and ductility.Furthermore,the mechanism of microstructure evolution and the correlation between microstructures and tensile properties were also discussed and clarified.展开更多
In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was cause...In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.52071319 and 51971060)the Foundation for Outstanding Young Scholar sponsored by Institute of Metal Research(IMR),the Foundation for Outstanding Young Scholar sponsored by the Shenyang National Laboratory for Materials Science(L2019F23)the Fundamental Research Project of Shenyang National Laboratory for Materials Science(No.L2019R18).
文摘A series of Alx(CoCrNi)100-x(x=0-21 at.%)medium-entropy alloys(MEAs)were designed and prepared to investigate the effects of Al addition on the microstructures and tensile properties.The results reveal that the lattice structure changes from the initial single FCC structure(x<10 at.%),to the FCC and disordered BCC structures(x=10 and 11 at.%),then to the FCC and BCC/B2 structures(11<x<21 at.%),finally to the duplex BCC/B2 structures(x≥21 at.%)with increasing Al addition.Consistent with microstructures,significant changes also occur in the corresponding tensile properties with Al addition,showing that the strength increases and the ductility decreases with increasing Al addition.Especially,the Al-15 MEA exhibits an acceptable balance of strength and ductility.Furthermore,the mechanism of microstructure evolution and the correlation between microstructures and tensile properties were also discussed and clarified.
基金financially supported by the National Basic Research Program of China(No.2014CB643603)the National Natural Science Foundation of China(No.51173178)
文摘In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.
