Behavior of Bismuth in Solidification of Lead-free Bronze and Effects of Bismuth on Mechanical Properties of Casting

Abstract

  Behavior of bismuth in the solidification process of lead-free bronze and effects of bismuth on the mechanical properties of the castings were studied. Bismuth existed at the finally solidified area in the bronze, and filled pores produced by the shrinkage of the bronze. During solidification, the bronze expanded according to the expansion of the bismuth. This volume expansion remarkedly appeared when the amount of bismuth addition exceeded that of pores. The tensile strength of the bronze decreased with increasing bismuth content due to the local stress around the bismuth in the casting. The decrease in tensile strength by bismuth addition reduced by the refinement of the bismuth size, because the decrease in the bismuth size reduces the stress field in the vicinity of the bismuth.