This paper deals with the effects of the addition of 0.00031, 0.00064, 0.001 and 0.0042 wt.% Bi on the matrix structure of ductile iron castings consisting of 7 sections of different thicknesses (3, 12, 25, 38, 50, 75 and 100 mm) and contain low content of Si (2.11 wt.%) and pearlite promoting element (0.018 wt.% Cu, 0.0055 wt.% Sn, 0.00041 wt.% Sb, 0.098 wt.% Mn). The Bi contents of 0.00031, 0.00064 and 0.001 wt.% were not significantly affected the share of ferrite and pearlite in the section thicknesses of 12, 25, 38, 50, 75 and 100 mm compared to the casting which does not contain Bi. In all these sections the share of pearlite was increased and the share of ferrite was decreased by the addition of 0.0042 wt.% Bi. All of the above-mentioned Bi contents were resulted in the formation of iron carbides in the section thickness of 3 mm. The share of carbides increases with increasing Bi content.
Direct observation of thermal effect appearance during grain boundaries complete wetting transition in copperbismuth system
Grain boundary wetting process takes place during the contact of solid metal phase with the metal melt. The liquid bismuth network formation along grain boundaries (GB) connected with wetting process was investigated in copper polycrystalline samples. The endothermic thermal effect in the temperature range close to complete GBs wetting transition temperature for Cu-Bi system was observed. Thermal effect size of GB wetting per mol of copper passed into bismuth melt during process of forming wetting GB channels was characterized as 21-23 kJ/mol.
The liquid bismuth network formation along grain boundaries (GB) and triple junctions (TJ) was investigated in copper polycrystalline samples. The experimental observation in situ technique of Bi penetration through the Cu plate was used. The temperature dependence of the penetration rate of the melt through the wafers of polycrystalline copper and the effective activation energy of penetration of Bi along the GBs are found.