Abstract
The grain refinement effects of Ir and Rh added to an equiaxed crystal of Ag-based casting alloys were investigated.The results were as follows: (1)To refine the crystal size, similar to Ir-addition, the maximum amount of Rh added to pure Ag were about 0.005wt%.An addition of Ir or Rh over that maximum amounts caused the formation of white part(second phase)without the refinement of grain size. (2)Grain refinement effects are related to equilibrium distribution cofficient(K)of solute elements.K of Rh in Ag-Rh alloy is thought for much than 1. (3)The grain refinement effects of Ir or Rh added to an equiaxed crystal of Ag-Pd alloys were affected by Pd content of the alloy.A basic amount of Ir to Pd content was about 1/50 and those of Rh was about 1/100, but the mechanical properties did not improved of Ir or Rh-addition.An addition of excessive amounts of Ir or Rh to the alloy caused deterioration of the mechanical properties, especially reduce the elongation of the alloy.
