Stability of Ni-based bulk metallic glasses

Several ternary (NixNbySnz) refractory alloy glasses (RAGs) were studied at elevated temperatures in order to assess the stability of the amorphous state, i.e. devitrification, and to identify subsequent phase transformations in these materials. differential scanning calorimetry (DSC) experiments indicated a complex phase transformation sequence with several distinct crystallization and melting events being recorded above the glass transition temperature, Tg. Below Tg the RAG samples were studied with an in situ environmental X-ray furnace facility, which allowed step-wise isothermal ramping experiments commencing at a temperature below the reduced temperature of T/Tg ≈ 0.80. Distinct crystalline phases were observed when T/Tg ≈ 0.84 for ternary RAG alloys, while similar experiments on Zr-based Vit 106 glass alloys did not reveal any apparent phase separation until T/Tg ≈ 0.96. The phase separation kinetics followed an Arrhenius type of relationship with Ni3Sn, and Nb2O5 being the principle crystalline precipitates.