Glass forming ability and crystallization behaviors of the Ti-Cu-Ni-(Sn) alloys with large supercooled liquid region

The thermal stability and crystallization behavior of melt spun amorphous Ti₅₀Cu₃₅Ni_15-xSn_x (x = 0, 3, 5, 7) alloys has been studied in by thermal analysis (DSC and DTA) and X-ray diffractometry. Partial replacement of Ni by Sn up to 5 at % in Ti₅₀Cu₃₅Ni₁₅ alloy improved thermal stability and glass forming ability. The onset temperature of the first exotherm increased from 739 to 756 K with increasing Sn content x from 0 to 5, and then decreased to 745 K for the alloy with x = 7 due to change in crystallization sequence. Melt spun amorphous Ti₅₀Cu₃₅Ni₁₂Sn₃ and Ti₅₀Cu₃₅Ni₁₀Sn₅ alloys exhibit ΔT_x exceeding 78 and 76 K, respectively, which is significantly larger than ΔT_x of 46 K in Ti₅₀Cu₃₅Ni₁₅ alloy. Amorphous Ti₅₀Cu₃₅Ni₁₅ alloy crystallized by precipitation of supersaturated cubic Ti(Ni,Cu) phase followed by decomposition into a mixture of TiCu and TiNi at higher temperature. Amorphous Ti₅₀Cu₃₅Ni_15-xSn_x (x = 3, 5) phase crystallized by precipitation of cubic Ti(Ni,Cu) phase, followed by transformation into a mixture of TiNi, TiCu, Ti₃Sn phases. Amorphous Ti₅₀Cu₃₂Ni₈Sn₇ phase crystallized by coprecipitation of cubic Ti(Ni,Cu) phase and unidentified phase, followed by transformation into a mixture of TiNi, TiCu, Ti₃Sn phases.