Distinctive Slow β Relaxation and Its Impact on Mechanical Property of LaCe Based Bulk Metallic Glasses

The slow β relaxation which occurring at temperatures far below glass transition temperature, typically playing important roles in the plastic deformation behavior of metallic glasses. Compared with polymer glasses, most of the metallic glasses do not exhibit obvious β relaxation based on dynamic mechanical analysis. In the current work, prominent β relaxation behaviors of a series (La_xCe_100−x) Al₁₀Co₂₅ (x = 50, 60, 70, 80) bulk metallic glasses (BMGs) at low temperature are observed using dynamic mechanical analysis. Compared with other BMGs, the LaCe based BMGs show a pronounced β relaxation peak and relative low peak temperature, the activation energy of the β relaxation based on Arrhenius equation are calculated around 79.3 kJ/mol to 86.4 kJ/mol, which obey an empirical rule that E_β ≈ (26 ± 4) RT_g, with the coefficient of 23. Experimental results from room temperature compression tests for the LaCe based BMGs indicate that low temperature activated β relaxation behaviors facilitate the good plasticity of the LaCe based BMGs.