Directional solidification of Ni-Ni₃Si eutectic in situ composites by electron beam floating zone melting

Combining the intermetallic compound with the ductile metal at the eutectic composition is one promising method to improve the ductility of the intermetallic compound. This paper reports the microstructure and the micro-hardness of the Ni-Ni₃Si eutectic in situ composites prepared by electron beam floating zone melting technique. Ni-Ni₃Si eutectic in situ composites display regular lamellar eutectic structure at the solidification rate R=0.3-4.0 mm/min. The lamellar spacing is decreased with the increase of the solidification rate. The phase composition of the Ni-Ni ₃Si eutectic in situ composites is also determined by X-ray diffraction. Ni-Ni₃Si eutectic in situ composites present lower micro-hardness than pure Ni₃Si, although a small quantity of metastable Ni₃₁Si₁₂ phase is formed during the directional solidification process.