Effects of Al and Ti additions on the thermal stability, glass-forming ability and mechanical properties of Ni60Nb20Zr20 glassy alloy

The glass-forming ability and thermal stability was investigated in a family of Ni-based alloys. The alloys were made by the addition of Al and Ti into Ni60Zr20Nb20. Upon Al addition, the supercooled liquid region (ΔTx), the reduced glass transition temperatures (Tg/Tl) and γ = Tx/(Tg + Tl) gradually increase with the increasing Al content. The maximum values of ΔTx = 54 K, Tg/Tl = 0.615, and γ = 0.405 are reached at the Ni60Zr20Nb15Al5 composition, which exhibits the largest GFA, and can be made into BMG rods of at least 3 mm in diameter. A further substitution of Nb by Ti can extend ΔTx from 54 to 70 K, and glassy alloy rods with 2 mm in diameter can be obtained for the alloys with Ti contents less than 10 at.%. Under uniaxial compression at room temperature, these new Ni-based BMGs exhibit high fracture strengths of 2775–2900 MPa and Young's modulus of 145–152 GPa. The Ni60Zr20Nb15Al5 BMG also exhibits a plastic elongation of 2.5%.