Thermal and microstructural study of slowly cooled Ni-B hard alloys containing Ti

Abstract

Binary Ni-B alloys containing varied amounts of titanium were prepared and investigated in this study. Differential Thermal Analysis (DTA) was used to study the solidification and transformation behavior of the alloys, while Optical Microscope (OM) and Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray Analyzer (EDXA) were used to study the microstructure of the alloys. Microscopic and thermal investigations of the alloys revealed the presence of two major primary phases Ni (α) and τ with other binary and ternary eutectic structures being present in the hard alloys. The addition of titanium to the Ni-B system enhanced the formation of the ternary phase τ, while solid-state eutectoid transformation of the τ phase was observed in alloys with low titanium composition. But such transformation was not detected in alloys with high titanium contents, which enhanced the formation of hard boride phases.