Crystallization of Zr-Ni metallic glasses

McKamey, C.G.; Kroeger, D. M.; Easton, D. S.; Scarbrough, J. O.

doi:10.1007/bf02431623

Cited by 24 publications

(5 citation statements)

References 23 publications

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“…For sintered samples, crystalline reflections appear overlaid the broad peaks of the amorphous phase. For G5, the main phase produced by devitrification is the metastable Ni 2 Zr 3 , [22] in equilibrium with tetragonal NiZr 2 , orthorhombic NiZr, and monoclinic ZrCu. Orthorombic Al 5 Ti 3 , metastable Ni 2 Zr 3 , tetragonal NiZr 2 and tetragonal CuZr 2 have been identified as the crystalline phases in G2.…”

Section: Resultsmentioning

confidence: 99%

Spark Plasma Sintering of a Zr‐Based Metallic Glass

et al. 2011

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Amorphous metallic alloys are among the most recent class of metallic materials. [1][2][3] Indeed, low glass forming ability (GFA) of major alloys induces manufacturing into thin ribbons shape (thickness < 100 mm) since the 1960s. The development of bulk parts with reasonable dimensions is more recent (early 1990s), and it still concerns small variety of alloys having high GFA. The formation of metallic glasses (MGs) is kinetically controlled and obeys empirical rules first stated by Inoue. [4] Many metals can be processed in MG form, such as Zr, Ti, Ni, or Fe, resulting in reasonable coverage domains of properties (mechanical, magnetic, resistance to corrosion, wear). [5][6][7] Amorphous alloys present neither long-range ordering nor structural defects and then do not experience homogenous distribution of defects for strain accommodation, like in crystalline alloys. In contrast, it follows that MG possess high strength close to the theoretical s max % E/20, no macroscopic ductility and high resilience owing to a moderate Young's modulus (similar to those of their crystalline counterparts) and an average 2% elastic deformation.Bulk MGs are essentially manufactured using casting and rapid quenching techniques, thus limiting shapes and dimensions of the available parts. [8] One promising way consists in manufacturing bulk parts from fine amorphous powders, even having a low GFA. [9] Atomization of MG powders have been studied since the early 1980s, [10] and attempts for sintering were carried out by extrusion, [11] hot pressing, [12] and more recently spark plasma sintering (SPS). [13][14][15][16][17][18][19] This paper reports on an analysis of SPS consolidation of a Zr 57 Cu 20 Al 10 Ni 8 Ti 5 MG produced by high-pressure gas atomization. This MG was extensively studied in its bulk form for its structure, thermal, and mechanical behavior and is then the relevant reference for comparison with sintered parts. [20,21] Systematic thermal and structural analyses of SPS consolidated powders with various grain sizes have been performed to identify specific SPS densification and consolidation mechanisms. Moreover, local transmission electron microscopy (TEM) analyses of the specimens point out occurrence, with clear evidences, of some physical events not observable in crystalline solids, as for example temperature overshoot revealed by partial devitrification. This study aims to approach the specific mechanisms of sintering through SPS of MGs, with particular interest in phenomena localized at the particle contacts (necks).

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Section: Resultsmentioning

confidence: 99%

Spark Plasma Sintering of a Zr‐Based Metallic Glass

et al. 2011

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“…6(a) for amorphous alloys formed by meltquenching. Later, Altounian et al [20] and McKamey et al [21] reported enthalpy of crystallization data of the same magnitude for Ni-rich alloys, but slightly (by about 1-2 kJ mo1-1) smaller on the Zr-rich side. The final crystallization products have been confirmed to be the equilibrium compounds [20].…”

Section: Experimental Datamentioning

confidence: 85%

“…Amorphous Zrl_~Mx alloys have been formed only by mechanical alloying of elemental Zr and A1 powders [17][18][19]. Amorphous Zr-Ni alloys on the other hand, have been formed by a variety of techniques [6(a), [20][21][22][23][24][25]. In Section 2 we first discuss the experimental enthalpy of crystallization data for amorphous Zrl_~klx and Zrl_xNix alloys, determined from calorimetric measurements, and convert them into enthalpy of formation data using the known enthalpy of formation for equilibrium compounds [6].…”

Section: E Ma M Atzmon / Zrt_alx and Zrl_xnix Alloysmentioning

confidence: 99%

Enthalpies of formation and crystallization of amorphous Zr1-xAlx and Zr1-xNix alloys: calculations compared with measurements

Atzmon

1993

Journal of Alloys and Compounds

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The enthalpies of formation of amorphous Zrl_~Mx and Zrl_xNix alloys have been calculated based on CALPHAD data and compared with experimentally determined values. A direct extrapolation of the thermodynamic functions of the undercooled liquid significantly underestimates the stability of the amorphous phase. When including the effects of the excess specific heat of the undercooled liquid, ACp, good quantitative agreement between the calculations and experimental data has been achieved, in particular for the Zr-Ni case. Using the same ACp functions, the enthalpy of crystallization of the amorphous alloys in both systems has been computed and found to agree well with the same quantity directly obtained from calorimetric measurements. These calculated enthalpy of crystallization data have also been employed in an alternative approach to calculating the enthalpy of formation of the amorphous alloys; such calculations are in excellent agreement with experimental values in both Zr-AI and Zr-Ni cases. It is shown that the enthalpy-composition diagram measured or calculated using our approaches can be used as a good approximation to the free energy-composition diagram in predicting the homogeneity range of the amorphous phase for low synthesis temperatures.

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“…These samples exhibit broad peaks, characteristic of nanocrystalline phases. For G5, the main phase is Ni 2 Zr 3 metastable [27] in equilibrium with tetragonal NiZr 2 , orthorhombic NiZr and monoclinic CuZr. Crystalline phases in G2 are orthorhombic Al 5 Ti 3 , metastable Ni 2 Zr 3 , tetragonal NiZr 2 and tetragonal CuZr 2 .…”

Section: Sps Of Mg Powdermentioning

confidence: 99%