Phase separation in Ni70Nb30−Y glasses

Abstract

Phase separated metallic glasses were prepared in the ternary Ni-Nb-Y system by rapid quenching of the melt. For Ni-rich alloys, early stage of spinodal decomposition or an almost homogeneous glassy state is obtained due to the reduction of the critical temperature of liquid-liquid phase separation near to the glass transition temperature. In situ small-angle X-ray scattering at elevated temperature gives evidence of on-going phase separation of the glass prior to crystallisation. The structural changes during isothermal heat treatment point to a spinodal mechanism of the decomposition. For glass with low Y-content (5 at %) no indication of phase separation is found in accordance with the composition dependence of the metastable miscibility gap of the supercooled liquid. Upon heating, the phase separated glass becomes a precursor and causes the nanostructure of the Ni2Y-phase formed as the first stage of crystallization. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

Locally fluctuating cooling rate as possible reason for non-crystalline plasticity in metallic glasses

“…Structural fluctuations on the 1-to-10 nm scale in metallic glasses have been reported in many publications, see, e.g. [13][14][15][16]. Different local packing, especially icosahedral and non-icosahedral arrangement, is often assumed to explain experimental data, see, e.g.…”

Atomic probe tomography and creep deformation studies of highly dynamic metallic systems: copper-zirconium based metallic glass alloys and tin-based alloy

“…Phase separation in metallic glass was observed in various systems [69,[88][89][90]. As the anomaly in DSC curves suggested, the best glass former composition, Cu 64 Zr 36 has the strongest shear strain rate dependency.…”

“…The melt spinning apparatus resembles that of rheometers with adapted geometries for measuring viscosity, shear modulus and other rheological quantities. Several publications reported on the rheological evidences of shear-assisted crystallization on simple and complex fluids such as polymer melts [67], colloidal glasses [64], bulk metallic glasses [68,69], molecular liquids [70], etc. There have been several proposals to explain the complex problems of shearinduced crystallization.…”