Effect of cooling rate on microstructure of B2-NiSc intermetallics


  • Zhipeng Yuan Henan Polytechnic University
  • Hao Chen Henan Polytechnic University
  • Hongbao Cui Henan Polytechnic University
  • Yatao Chang Henan Polytechnic University
  • Xuefeng Guo Henan Polytechnic University


centrifugal casting, B2-NiSc, microstructure evolution, rapid solidification, heat treatment, (Ni2Sc NiSc)eutectic


Ni-50at%Sc alloy was prepared by centrifugalcasting method. Volume fraction, the actualcontent of B2-NiSc and second phase Ni2Sc inalloy were analyzed with an Image-Pro Plussoftware. The cooling rates for the solidified thinplate with thickness of 2.65mm, 1.2mm, 0.75mmand 0.35 mm are 1164, 2570, 4112 and 8811 K·s-1, respectively. It is found that d=0.5 mm was ancritical dimension which corresponds to an abruptchange in the solidification rate. It is also foundthat (Ni2Sc+NiSc)eutectic was dispersed at grainboundary or between dendritic arms due to the lossof Sc element during melting. While d? 0.5mm(corresponding to the thin plate with thickness of0.75mm, 1.20mm and 2.65 mm), the solidificationstructure consists of primary phase B2-NiSc and(Ni2Sc+NiSc)eutectic. While d ? 0.5mm(corresponding to the thin plate with thickness of0.35 mm), the solidification structure is composedof fine globular B2-NiSc and relatively smallamounts of (Ni2Sc+NiSc)eutectic. Based on the phasevolumetric analyzing of the microstructure with anImage-Pro Plus software, the loss of Sc elementduring melting was about 3.01~3.10 at%. Theeutectic NiSc in the lamellar eutectic structuretogether with the primary phase B2-NiSc form alarger single phase NiSc, while Ni2Sc with the formof particles is distributed on the grain boundariesafter (970 ?, 72 h) homogenization heattreatment.