Crystallization Behavior Of Amorphous Alloys Research Articles

Interface characteristic of Zr-based metallic glass and copper by laser pulse welding

The crystallization behavior of amorphous alloys during welding is more complex than that of traditional metals. In this paper, the Zr-based amorphous alloy and copper crystals were welded by pulsed laser butt welding method, the crystallization behavior of the amorphous alloy/crystalline metal welding interface is deeply studied. The results show that Zr2Cu and Zr2Ni crystal phases appear at the interface between Zr based amorphous alloy and copper, and a Cu rich region is formed at the amorphous side of the interface. A small amount of Zr, Ni, Ti diffuses to the Cu side, forming ZrO2, TiO2, CuO and other oxides on the surface of the sample. These oxides will cause changes in the voltage potential at the interface.

Beating Homogeneous Nucleation and Tuning Atomic Ordering in Glass-Forming Metals by Nanocalorimetry.

In this paper, the amorphous Ce68Al10Cu20Co2 (atom %) alloy was in situ prepared by nanocalorimetry. The high cooling and heating rates accessible with this technique facilitate the suppression of crystallization on cooling and the identification of homogeneous nucleation. Different from the generally accepted notion that metallic glasses form just by avoiding crystallization, the role of nucleation and growth in the crystallization behavior of amorphous alloys is specified, allowing an access to the ideal metallic glass free of nuclei. Local atomic configurations are fundamentally significant to unravel the glass forming ability (GFA) and phase transitions in metallic glasses. For this reason, isothermal annealing near Tg from 0.001 s to 25,000 s following quenching becomes the strategy to tune local atomic configurations and facilitate an amorphous alloy, a mixed glassy-nanocrystalline state, and a crystalline sample successively. On the basis of the evolution of crystallization enthalpy and overall latent heat on reheating, we quantify the underlying mechanism for the isothermal nucleation and crystallization of amorphous alloys. With Johnson-Mehl-Avrami method, it is demonstrated that the coexistence of homogeneous and heterogeneous nucleation contributes to the isothermal crystallization of glass. Heterogeneous rather than homogeneous nucleation dominates the isothermal crystallization of the undercooled liquid. For the mixed glassy-nanocrystalline structure, an extraordinary kinetic stability of the residual glass is validated, which is ascribed to the denser packed interface between amorphous phase and ordered nanocrystals. Tailoring the amorphous structure by nanocalorimetry permits new insights into unraveling GFA and the mechanism that correlates local atomic configurations and phase transitions in metallic glasses.

Curie temperatures and crystallization behavior of amorphous Fe 81−xNi xZr 7B 12 (x=10, 20, 30, 40, 50, 60) alloys

Curie temperature, crystal structure and crystallization behavior of amorphous alloys with the stoichiometry Fe 81− x Ni x Zr 7B 12 ( x=10–60) have been studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and AC-magnetization (TMAG) measurements as functions of temperature. The thermal stability of long-range magnetic order, T C vs. Ni content in as-quenched amorphous alloys exhibits maximum at 352 °C for x=40. The primary crystallization has been detected during annealing at the first crystallization stage of all ribbons investigated.

MAGNETIC PROPERTIES, ELECTRICAL RESISTIVITY AND CRYSTALLIZATION BEHAVIOR OF AMORPHOUS Fe90-xBxZr10 ALLOYS

The effects of B content on the magnetic and electrical properties and crystallization behavior of amorphous alloys based on FeZr are studied in this paper, and compared with amorphous FeB alloys. The reasons of the average magnetic moment per FeZr atoms. μFeZr and Curie temperatures Tc increase with increasing B content are explained. Finally, the scattering mechanisms of electrical resistivity at various temperatures and effects of B or Zr element on the crystallization temperature in these alloys are discussed.