Alexander Yu. Churyumov

Nanostructured Zr-Pd Metallic Glass Thin Film for Biochemical Applications

Zr-Pd metallic glassy thin films with a hierarchical nano-scale structure, produced by magnetron sputtering of the Zr and Pd powder mixture, demonstrate a unique combination of physical and biochemical properties. Thermal stability of the nano-structured glassy samples, their resistance to oxidation in dry air and phase transformation behavior are discussed in the present work. These binary alloy samples also show exceptionally high corrosion resistance and spontaneous passivation in a simulated body fluid. Experiments on the catalytic activity and biocompatibility of this nanostructured metallic glass indicate that this is a very suitable material for biochemical applications. Compared to the multicomponent alloys studied earlier this binary alloy has much simpler chemical composition, which makes preparation of the sample with defined stoichiometry easier, especially when the elements have different sputtering rates.

On cryothermal cycling as a method for inducing structural changes in metallic glasses

The influence of cryothermal treatment on the mechanical properties of metallic glasses with different compositions was investigated in the present work. It was found that cryothermal cycling can induce rejuvenation as well as relaxation of the metallic glasses. The local apparent Young’s modulus and its spatial distribution width on the surface of the metallic glass increase after cryothermal cycling, while in the bulk the effect depends on the glass composition. It appeared that this increase is temporary and disappears after a period of room temperature aging. This effect is connected with a large distribution of relaxation times in the metallic glasses due to their heterogeneous structure and the formation of complex native oxides on the outer surfaces of the glasses. Our findings reveal that a cryothermal cycling treatment can improve or degrade the plasticity of a metallic glass, and the atomic bond structure appears to be very important for the outcome of the treatment.Metallic glasses: cryothermal cycling affects plasticityCryothermal cycling affects the structure and mechanical properties of metallic glasses in ways that depend on their composition. These metallic alloys, with their disordered atomic structures, have promising characteristics but before widespread applications are possible their behavior needs to be better understood. An international team of researchers led by Sergey Ketov from the Erich Schmid Institute of Materials Science, Leoben, Austria, have now subjected three such glasses with the general formula Zr60Cu20M10Al10 (where M is iron, cobalt or nickel) to temperature cycles between 77 and 320 K. The treatment was found to temporarily increase their surface stiffness, to a greater extent for the iron-based sample. It also affected their bulk plasticity: an increase was noticed for the iron-based glass, “rejuvenating” the material, whereas the cobalt-based glass was degraded and the nickel-based glass remained largely unaffected.Cryothermal cycling can induce rejuvenation as well as relaxation of metallic glasses. The surface apparent Young’s modulus and its spatial distribution width increase after the treatment, while in bulk effect depends on the glass composition. This increase is temporary and disappears after some time of room temperature aging. Effect is connected with a large distribution of relaxation times in metallic glasses due to their heterogeneous structure and the formation of complex native oxide on the glass surface. Cryothermal cycling can improve or degrade the plasticity of metallic glasses and the atomic bond structure determines the outcome of the treatment.