Amorphization and metastable polymorphs of ordered intermetallics Zr₃Al and Ni₃Al

Abstract

Observations of various metastable crystalline and amorphous polymorphs of Ll 2 -type intermetallics Zr 3 Al and Ni 3 Al are summarized. The difference in the tendency of these two alloys to become amorphous is obvious. Regardless of the nonequilibrium routes employed for synthesis and processing, amorphous Zr 3 Al is obtained easily, while amorphization of Ni 3 Al is rare. An analysis of thermodynamic and kinetic factors responsible for the observed polymorph selection and amorphization behavior is presented. The inadequacy of a simplified model proposed earlier is also discussed.

In situ TEM study of deformation-induced crystalline-to-amorphous transition in silicon

“…39,40 Our current study provides direct evidence of this mechanism, through in situ observation of the CAT process from its beginning (pristine crystal) all the way to the end (collapse into the amorphous phase).…”

Enthalpy of formation of intermetallic phases from Al–Zr system determined by calorimetric solution method

“…Due to overcooling, amorphous structure in alloys occurred. Tendency to the formation of amorphous phases during overcooling on the example of AlZr 3 was presented by Ma [8]. Samples were submitted to long-lasting annealing at elevated temperature.…”

“…Some of them have found practical application long time ago, e.g., NiAl for coating materials or Ni 3 Al for high-temperature structural materials [3][4][5]. Others, like aluminum-zirconium intermetallics, may be potentially applied in thermal nuclear reactors [6,7], also extensive work on the Al-Zrbased amorphous and nanocrystalline alloys has been reported [8][9][10]. Phase Al 3 Zr is desirable candidate for high-temperature structural applications [1,2].…”

Disorder–order phase transformation in sputter deposited Pd3In thin films

“…Sputtering deposition, one of the widely used thin films preparation methods, can also lead to the formation of metastable phases. For example, metastable or amorphous phases were also found in the sputter deposited NiMn [4][5][6], PtMn [7], PtPdMn [8], and Ni 3 Al [3,9] films. While stoichiometric Pd 3 In is stable up to 1223 • C [10], it was found in the previous studies [11][12][13] that Pd 3 In alloys with ordered tetragonal structure transformed into disordered face centered cubic (fcc) phase by plastic deformation and became ordered upon subsequent annealing.…”

“…Metastable phases can form through highly nonequilibrium processes such as rapid quenching from the melt, vapor condensation, severe mechanical deformation, and will transform to stable phases when annealing at higher temperatures [1,2]. For example, metastable polymorphs and amorphous phase were found in Ni 3 Al and Zr 3 Al through different nonequilibrium methods such as vapor deposition, ion or electron irradiation of ordered compounds, ion mixing of multilayers, mechanical alloying of elemental powders and mechanical attrition of ordered compounds [3]. Sputtering deposition, one of the widely used thin films preparation methods, can also lead to the formation of metastable phases.…”