Effect of Alloying Elements on Monotectic Composition of Lead Free Bronze with Dispersed Sulfide Particles

摘要

The lead free bronze with dispersed sulphide particles is one of the substitute materials for leaded bronze, which is used for water supply equipment, and the production number has been increased. The effect of sulphur content on the mechanical and machining properties has been reported, and the properties depend on microstructure of sulphide particles. The sulphide particles are shaped spherical due to metastable monotectic reaction although eutectic reaction is stable. However, the monotectic composition is not very clear although the microstructure depends on monotectic composition.In this article, the monotectic composition of the lead free bronze, which is Cu-Sn-Zn-Ni-S system alloy, has been evaluated by a theraiodynamic calculation and microstractural analysis of the alloy castings. The CalPhad method was applied for the thermodynamic calculation, and the monotectic compositions were calculated by changing amount of tin, zinc, and nickel as the alloying elements. The microstractural analysis was carried out by evaluating shape and size of sulphide particles in optical microstructures. A suitable monotectic composition is discussed from shape and size of sulphide particles in microstructure related with mechanical and machining properties of the alloy.