Low temperature mechanical properties of bulk metallic glasses

Compression tests have been performed for bulk metallic glasses of La55Al25Ni20 (L-glass) and Zr41Ti15Ni12CU11Be21 (Z-Glass) at temperatures from 4.2 K up to above the glass transition temperature. Shear fracture stresses are scattered between 0.75 GPa and 1.2 GPa in the L-glass, and between 1.3 GPa and 2.2 GPa in the Z-glass with a tendency of decrease towards both higher and lower temperatures from 77 K in L-glass and from 300 K in Z-glass. The normalized shear fracture stresses with respect to the Young's modulus are around 0.02 in both glasses. The micro-plastic strain measured with the strain gauge for the L-glass is about 0.2% at the shear fracture stress at room temperature, decreases with decreasing temperature and is of the order of 0.01% below 77 K. The mechanism that determines the shear fracture stress is discussed.