Stoichiometric Quantification of the Amorphous Precursor in the Mg-Ni System

Microstructural evolution during mechanical alloying of Mg and Ni

“…The details of the formation of this amorphous phase are discussed next. Nevertheless, as the milling time increases, more and more Mg reacts to form the amorphous phase, in agreement with previous works [11].…”

“…2). Using the Sherrer's method to measure the grain size, samples milled using a BPR of 4:1 had a Mg grain size of less than 10 nm after 22 h [25]. However, the Sherrer's method could not be applied to measure Mg grain sizes in samples milled using BPRs of 10:1 or 20:1 because the XRD peak broadening did not meet all the requirements for it to be valid.…”

“…The Mg 2 Ni compound can combine with hydrogen to form the Mg 2 NiH 4 hydride, which in turn has a lower hydration capacity than Mg, 3.6 wt.% H, but a much faster hydration kinetics [9,10]. Regarding materials processing, Mg 2 Ni has been traditionally produced by fusion, and hence it is difficult to obtain high quality Mg 2 Ni because of the large differences in melting point and vapor pressure between Mg and Ni [11]. However, it is now possible to avoid the inherent difficulties of the fusion technique by using mechanical alloying [3,[12][13][14].…”

“…However, in spite of the amount of work done since then, the sequence of events leading to the formation of the amorphous phases during mechanical alloying is still under discussion [22][23][24]. In the particular case of the Mg-Ni system, the existence of an amorphization process during mechanical alloying has also been detected [25,26]. Although it has been postulated that the amorphous phase may act as a precursor for the crystalline compound, the role that the initial elements play on the formation of this new amorphous phase is not completely understood yet.…”

Efecto del tiempo de molienda sobre la estabilidad termica del amorfo Mg₅₀Ni₅₀ producido mediante aleado mecánico

“…Pero su fabricación por métodos convencionales de fusión-solidificación tiene serios inconvenientes, debido a la gran diferencia de temperaturas de fusión de los elementos involucrados, la descomposición peritéc-tica que presenta el sistema, la gran presión de vapor del magnesio y su fuerte afinidad por el O 2 . En este contexto, el proceso de aleado mecánico (AM) desarrollado por Benjamin et al [2 y 3] en la década del 70, abre una posibilidad para la fabricación de este tipo de aleaciones, debido a que todo el proceso se desarrolla en estado sólido [4][5][6] .…”