Achieving Superior Strength and Ductility of Cu-Alloyed Ductile Iron via Sn Microalloying

Abstract

Ductile iron with high strength and elongation has a wide application in advanced equipment manufacturing industry. Copper (Cu) is a low-cost and highly effective alloying element, which is commonly used to prepare high-strength ductile cast iron materials. However, the single addition of Cu in stabilizing and refining pearlite is insignificant, and the combination addition of Cu and tin (Sn) can apparently improve the pearlite content and refine the pearlite lamellar spacing. In this paper, Sn was used for microalloying on Cu-alloyed ductile iron. The results show that with the Sn increases from 0 to 0.07 wt.%, the nodularity of the sample increases from 81.4 to 92.1%, the graphite particle size decreases from 46.4 to 33.6 μm, and the number of graphite particles increases from 167 to 257 pcs/mm². The pearlite content in ductile iron with 0.07 wt.% Sn addition is 98.9%, and the pearlite lamellar spacing is 172 nm. The Cu-alloyed ductile iron containing 0.04 wt.% Sn with best mechanical properties, and the ultimate tensile strength(UTS), yield strength(YS), elongation(EL) and Brinell hardness were 772, 540 MPa, 7.8% and 248 HBW, respectively. The reason for the high strength and elongation of Cu, Sn composite alloying ductile iron is due to the good graphite morphology, high nodularity and fine graphite particles, and the pearlite is effectively refined.