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 (Delta T-x), the reduced glass transition temperatures (TITI) and gamma = T-x/(T-g + T-1) gradually increase with the increasing Al content. The maximum values of Delta T-x = 54K, T-g/T-1 = 0.615, and gamma = 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 Delta T-x 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%. (C) 2007 Elsevier B.V. All rights reserved.