Deformation behavior of bismuth–tin alloy wires with eutectic morphology produced by the Ohno continuous casting process

Abstract

The Ohno continuous casting (OCC) process has been used to generate 62% Bi–Sn alloy wires approximately 2 mm in diameter with eutectic morphology at speeds between 30 and 387 mm/min. The microstructure was examined and tensile tests performed for wires cast at various speeds. The deformation behavior was investigated by observing the surface structure of wires at various tensile deformation stages. It was found that the eutectic morphology was of a quasi complex-regular structure for wires cast at higher speeds, whereas at lower speeds it contained a remnant of Chinese script type structure. It was found that bismuth fracture begins before inter-phase cracking in the initial stages and proceeds concurrently with inter-phase cracks in the latter part of the deformation process, allowing the accommodation of large strain. For wires cast at higher speeds, the inter-phase cracks play a leading role in wire fracture, whereas for wires cast at lower speeds, the bismuth fracture exerts a leading role in crack propagation and fracture. This difference was manifested in the fracture surface and elongation value.