Glass is a nonequilibrium state that continually relaxes toward a metastable equilibrium state by structural rearrangements.What is mysterious is that its past state is always memorized,viz.,showing memory effect.Glass exhibits disordered structure and anomalous atomic vibration as compared to ordered crystals,and this anomaly is termed as a boson peak.These two features,both are central to the understanding of glass,are generally investigated separately.
In this paper, we report a strain rate related glass transition in model SrCaYbMg（Li）Zn（Cu） metallic glasses at room temperature. A critical strain rate, equivalent to glass transition temperature, is found for the strain rate induced glassy state to liquid-like viscoplastic state translation. The results show that the observation time, equivalent to temperature and stress, is a key parameter for the transition between the glass and supercooled liquid states. A three-dimension glass transition diagram involved in time, temperature and stress in metallic glasses is established.
As a novel class of metallic materials, bulk metallic glasses(BMGs) have attracted a great deal of attention owing to their technological promise for practical engineering applications. In nature, biological materials exhibit inherent multifunctional integration, which provides some inspiration for scientists and engineers to construct multifunctional artificial materials. In this contribution, inspired by superhydrophobic self-cleaning lotus leaves, multifunctional bulk metallic glasses(BMG) materials have been fabricated through the thermoplastic forming-based process followed by the SiO_2/soot deposition. To mimic the microscale papillae of the lotus leaf, the BMG micropillar with a hemispherical top was first fabricated using micro-patterned silicon templates based on thermoplastic forming. The deposited randomly distributed SiO_2/soot nanostructures covered on BMG micropillars are similar to the branch-like nanostructures on papillae of the lotus leaf. Micro-nanoscale hierarchical structures endow BMG replica with superhydrophobicity, a low adhesion towards water, and self-cleaning, similar to the natural lotus leaf. Furthermore, on the basis of the observation of the morphology of BMG replica in the Si mould, the formation mechanism of BMG replica was proposed in this work. The BMG materials with multifunction integration would extend their practical engineering applications and we expect this method could be widely adopted for the fabrication of other multifunctional BMG surfaces.
We show that the diverse dynamic responses of viscosity of the supercooled liquid near the glass transition temperature can be inherited to glassy state and expressed in the discrepancy of stress relaxation, demonstrating a structural heterogeneous basis for fragility. The metallic glasses with diverse dynamics and structural heterogeneities manifesting in different densities and distributions of flow units can be classified and characterized in terms of a parameter n, which can be readily determined through stress relaxation method and is comparable to the kinetic fragility m of the supercooled liquid. The parameter can classify diverse metallic glasses and also benefits for understanding the correlation between the structural and dynamical heterogeneities of the metallic glasses.
