关键词: 结构, 球状石墨, 铸铁

Abstract: 　　By SEM observation on various types of spheroidal graphite (SG), it has been found that SG possesses a flake-like or a nodular nucleus and the duplex SG with a circumferentially growing interior spherulite and a spirally growing outer shell exists in both rare-earth-treated and magnesium-treated SG cast iron, and a structure model of the duplex SG has been proposed. It is then suggested that SG grows generally in a manner that a graphite flake growing in α-direction is twisted by twin/tilt with the (0001) plane as the growing interface, and the c -direction spiral branches then grow out, whereas the radial, the ribbed and the onion-type SG are special types of the duplex SG.

Key words: Cast iron, Spheroidal graphite, Structure