Evolution of TaC morphology during directional solidification of Ni, Cr, Al-TaC in-situ composite
(1.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China2.College of Chemistry and Chemical Engineering, Inner Mongolia University, Huhhot 010021, China3.Department of Superalloys, Institute of Metal Research, Chinese Academy of Sciences,Shenyang 110016, China4.School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
Abstract: The Ni, Cr, Al-TaC composite was directionally cast from a nickel-base alloy with a nominal mass composition of Ni-10Cr-5.0Al-13.9Ta-0.9C (mass fraction, %). The morphologies of TaC in the in-situ composite was observed with AMRAY100B SEM. TEM investigations were preformed in a JEM2000CX instrument at 150kV. The experimental results show that TaC fibers are grown from the dendritic arms of the primary blocky TaC in the bottom of the directionally solidified Ni, Cr, Al-TaC sample. The longitudinal growth of TaC fibers is controlled by the pyramid growth mechanism under forced heat flow of [001] orientation. The transverse growth pattern of TaC is markedly affected by the unstable mode. The multiplicity of TaC transverse morphologies is presented.
Key words: composite； TaC； fibers； crystal growth； directional solidification