Superplasticity in La_(55)Al_(20)Ni_(25) Metallic Glass

摘要

We investigated the mechanical properties of glassy solid and supercooled liquid in a La_(55)Al_(20)Ni_(25)(at.%) metallic glass that has a wide supercooled liquid region of 65 K before crystallization. The supercooled liquid above the glass transition temperature (T_g) exhibited superplastic-like behavior during isothermal tensile deformation at strain rates in the range of 10~(-4) s~(-1) to 10~0 s~(-1). The maximum elongation to failure was in excess of 1800 % at a strain rate of 5.0×10~(-2) s~(-1) and at 503 K (T_g+20 K, 0.71T_m) under about 40 MPa. The supercooled liquid of the metallic glass exhibited a strain-rate sensitivity exponent (m value) of nearly 1.0. The superplasticity of the La_(55)Al_(20)Ni_(25) metallic glass was superior to that of the Zr_(65)Al_(10)Ni_(10)Cu_(15) metallic glass. The metallic glass, moreover, have many advantages in the superplastic deformation as compaered with polycrystalline superplastic materials.