On segregation of Zr and wettability of active Ag-Cu-Zr alloy on cubic boron nitride surface

Eutectic 72Ag28Cu alloy finds it difficult to form chemical bond with single crystal cubic boron nitride (cBN) and to wet its surface when it contains highly reactive Zr as an active element, in place of Ti. For revealing the underlying science, AgCu4Ti4Zr is melted on cBN surface and interfacial reaction phases are probed. Only nitrides and borides of Ti are detected but without any Zr-based product. Zr segregation towards cBN is severely impaired, causing such failure to form chemical interface and wet cBN surface. Atomic radius, activity coefficient, Gibb's free energy of mixing and partial molar enthalpy are found to be influencing factors.