Structure and mechanical properties of as-cast (ZrTi)100−xBx alloys

Abstract

The microstructure, mechanical properties, and fracture characteristics of (Zr50Ti50)100−xBx alloys (x=0, 0.5, 1, 2at.%) obtained by casting were investigated. Trace additions of boron (B) to the Zr50Ti50 alloys induced significant microstructural changes. Changes included the promotion of dendritic growth and refinement in prior-β grain and α′-lath size. Large numbers of stacking faults were also observed in ZrB2 and TiB intermetallics. The location of B atoms and the lattice mismatch energy between intermetallics and matrix were responsible for the stacking faults. (ZrTi)B alloys demonstrated higher tensile strength than matrix material. Both the intermetallics with high strength and modulus and the grain refinement played important roles in improving the mechanical properties of alloys. This result could be explained in terms of a shear-lag model based on the load transfer concept and Hall–Petch mechanism. The elongation-to-failure of (ZrTi)B alloys decreased with increased B concentration. The reduction in elongation-to-failure of (ZrTi)B alloys could be attributed to the presence of ZrB2 and TiB intermetallics and refinement of α′-laths.