Effect of the growth parameters on the Ni–Ni 3Si eutectic microstructure

Abstract

Microstructure of the Ni–Ni 3Si eutectic system from the nickel rich portion of the nickel–silicon phase diagram was studied as a function of the growth conditions and parameters. In the as-solidified condition the microstructure presents a high degree of regularity and uniformity, with an orientation clearly dependent on the heat flux direction. Directional solidification processing in the range of the growth rates from 6.5 to 20 mm/h resulted in a highly regular polycrystalline structure. The dominant morphology was well aligned and lamellar, without any eutectic cells or dendrites. Also, it was observed that its growth mode is highly dependent on the growth rate, since the increase in the growth rate resulted in a decrease in the interphase spacing and microstructure refinement. During hardness testing material exhibited lower hardness than pure Ni 3Si, suggesting improvement in ductility.