Abstract
The present study was carried out on B319 alloy modified with about 180 ppm Sr. To this alloy, Ca (0–500ppm) and Bi (0.1–1.0%) were added. Their deleterious effects on the eutectic Si characteristics (as-cast and solution heat-treated conditions) as well as tensile properties under the same conditions plus T6 temper were investigated. The results show that Ca addition up to 500 ppm leads to partial modification, whereas applying 0.1%Bi causes almost complete un-modified structure. Further addition of Bi has no marked effect. Calcium–Mg and Bi–Mg interactions would lead to a significant deterioration in the three tensile parameters of the base B319 alloy, i.e., 30 MPa and 60 MPa in UTS (T6 temper) for 0.05%Ca and 1.0%Bi additions, respectively, about 45 MPa in YS, and almost 100% in ductility (no improvement). Apparently, B319 alloy containing less than 100 ppm Ca or about 0.5%Bi produces the best Q values in the solution heat treated and the T6 conditions. The main fracture behavior of these alloys was the formation of fine dimple structure with Ca or Bi particles imbedded at their interiors.