Precipitation Behavior of Thermo-Mechanically Treated Ti₅₀Ni₂₀Au₂₀Cu₁₀ High-Temperature Shape-Memory Alloy

In the present work, precipitation behavior of TiNiAuCu-based high-temperature shape-memory alloys is studied. Two alloys with compositions Ti₅₀Ni₃₀Au₂₀ and Ti₅₀Ni₂₀Au₂₀Cu₁₀ were prepared. After 30 % cold rolling, both alloys were then annealed at different temperatures. Formation of Cu-rich TiAuCu and Ti-rich Ti₃Au precipitates was observed in Ti₅₀Ni₂₀Au₂₀Cu₁₀ alloy when annealed at different temperatures after cold deformation. It was noticed that prior cold deformation has significant effect on the precipitation behavior. A similar kind of precipitation behavior has been previously reported in TiNiPdCu alloys. Both TiAuCu and Ti₃Au type precipitates were found to be deficient in Ni content which causes an increase in Ni content of the matrix and a small decrease in transformation temperatures of the Ti₅₀Ni₂₀Au₂₀Cu₁₀ alloy.