Development of new ductile iron with super-high thermal conductivity and elongation

The effects of Si content,graphite volume fraction and pearlite volume fraction on the thermal conductivity of ductile iron were studied based on theoretical model analysis.Calculated results showed that the thermal conductivity of ductile iron was more sensitive to Si content compared with the volume fractions of pearlite and graphite.The key method to design and develop high thermal conductivity ductile iron was to control the Si content.Within 0.9-2.2 wt.%Si content,experimental results showed that with the increase in Si content,the thermal conductivity of ductile iron decreased dramatically,and the yield strength and tensile strength of ductile iron almost linearly increased,but the elongation remained almost unchanged.The dependence of thermal conductivity of ductile iron on temperature changed from monotonic decreasing to increasing first and then decreasing.Finally,we broke the common composition range of ductile iron and designed a new high C(≥3.9 wt.%)and low Si(1.0-1.4 wt.%)ductile iron with super-high thermal conductivity and elongation.Its thermal conductivity exceeded 40 W/(m K)within 27-300℃,and maintained at 35-40 W/(m K)at 500℃.The elongation was over 25%,and the tensile strength was more than 300 MPa.