Formation, structure, and crystallization of Al-rich metallic glasses

Abstract

The formation, structure, and the crystallization of Al85YxNi15−x are studied using x-ray diffraction and differential scanning calorimetry. The results show two distinct glasses depending on composition. Y-rich glasses (x≥8) are homogeneous with a well-defined glass transition. The x-ray diffraction patterns have a single main peak. These glasses crystallize through a nucleation and growth process. Y-poor glasses (x<8) do not show a glass transition and have a shoulder on the high-angle side of the main peak in their x-ray diffraction patterns. We show that the shoulder peak is due to quenched-in Al nuclei. These glasses are shown to crystallize through the growth of these nuclei. Y-rich glasses (x≥8) are more stable as demonstrated by the presence of the glass transition and their higher crystallization temperature, enthalpy, and activation energy. The occurrence of a prepeak for all compositions is attributed to Y-Y pairs.

Phase Transformations in Al<SUB>87</SUB>Ni<SUB>7</SUB>Ce<SUB>6</SUB> and Al<SUB>87</SUB>Ni<SUB>7</SUB>Nd<SUB>6</SUB> Amorphous Alloys

“…Ternary alloys with Nd behave as those containing Gd 5) and Y. 9) Preliminary results of the authors' group show a similar crystallisation sequence for an alloy with RE = Sm but another with RE = La is alike Al 87 Ni 7 Ce 6 .…”

“…The explanation for the main composite halo is controversial. It was attributed to contribution to the total diffracted intensity from very short Al-TM distance, 9) at variance to the possibility of amorphous phase separation 10) or to the presence of quenched-in Al nuclei.…”

Study on crystallization of nanocrystalline/amorphous Al-based alloy

“…1), which is considered as indication of the existence of short-range order (SRO) in the sample. Previous work showed that the pre-peak corresponding to chemical short-range order (CSRO) of clusters [21][22][23][24][25][26][27][28], which was observed in XRD patterns of most Al-based amorphous alloy, was ascribed to the strong effect among different atoms in alloys and helpful to the formation and stability of amorphous Al-based alloys. In Al-Fe-X alloy, the pre-peaks in XRD patterns correspond to Al-Fe clusters with strong CSRO.…”

Calorimetric study of enthalpies of mixing in liquid (aluminium–gallium–yttrium) alloys

“…Four rare-earth ternary intermetallide compounds have been found on the isothermal sections of the system at T = 673 K [10], namely: Y(Al x Ga 1 À x ) 4 (0.65 < x < 0.6875), Y(Al x Ga 1 À x ) 4 (0.4 < x < 0.475), YAl 0.4 Ga 2.6 , Y(Al x Ga 1 À x ) 2 (0.35 < x < 0.45). In addition, regions of solid solution, which form with substitutions of Al on Ga and vice versa in the YAl 3 , YAl 2 , YGa 6 and YGa 2 intermetallide compounds, have been determined in the ternary system [10]. The magnetic susceptibility of the Y(Al x Ga 1 À x ) 4 compounds have also been reported in [11].…”

“…Amorphous ternary Al-Y-TM (TM -Fe, Ni, Co) [3][4][5][6] and quaternary Al-Y-TM-TM alloys [7][8][9] have large compositional ranges of glass formation, high glass-forming ability, excellent shape formability, good ductility of bending and high corrosion resistance. It is known that a simultaneous dissolution of Ga and Al is an effective method to extend supercooled liquid region and to decrease liquidus temperature of the alloys, which increases glass-forming ability.…”