Al70-XSi30MnX (X=0, 3, 5, 7, 10, mol%) ribbons were prepared by melt spinning. A supersaturated solid solution of Si and Mn in fcc Al and some microstructures consisting of nano grains were obtained. Some alloys with nano-sized grains exhibited high discharge capacities and favorable cycle properties. The capacity of more than 400 mAh/g could be obtained in melt-spun Al67Si30Mn3 alloy after 20 cycles and more than 300 mAh/g after 40 cycles. Li/Si and Li/Al compounds in the anodes of pure Al and pure Si were not detected in Al-Si-Mn alloys inserted by Li. It is considered that the formation of the supersaturated solid solution and refinement of microstructures have prevented the alloys from the forming the compounds with superfluous Li. As a result, the electrochemical properties have been improved.
SUN ZhanBo1, LI XuePeng1, WANG XiaoDong1, HU Qing1, ZHAO MingShu1, ZHU YaoMin2, LI Yan2 & SONG XiaoPing1 1 School of Science, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China
The ribbons of Cu-Cr alloys with high Cr content (15%- 35%, mass fraction) were prepared by rapid solidification. The microstructures of solidified samples were analyzed by scanning electron microscopy and transmission electron microscopy. The results reveal that a representative liquid phase separation microstructures are observed in Cu75Cr25 ribbons solidified at a cooling rate of about 104K/s. The liquid phase separation is not restrained when the cooling rate is enhanced to about 107K/s. However, the size of Cr particles solidified from Cr-rich liquid or Cr-rich regions in alloy melts could be refined by increasing the cooling rates. The size of Cr particles increases with increasing Cr contents when the ribbons contain 15% to 35%Cr.
The microstructure and resistivity of melt-spun CuCrTi ribbon were studied.The results reveal that the maximal size of theprimary Cr particles in the microstructures is below 100 nm by 0.65%-3.8%Ti(mole fraction)addition and the resistivity of annealedribbons of 0.65%-1.3%Ti addition can meet the need of the contact materials used by the medium-voltage vacuum interrupters.Bycontrasting the melt-spun microstructures to the annealed microstructures,the primary Cr particles do not grow up quickly in theannealing process.The X-ray diffraction studies reveal that alloying increases the amount of the solute in Cu and Cr phases andresults in the increase of resistivity.By the thermodynamic analysis,adding Ti to CuCr29 alloys increases the critical supercooling ofthe liquid/solid transformation,which makes the critical radius of nucleation decrease and the rate of nucleation increase.As a result,the microstructure of CuCr ribbon can be further refined.
