Effect of cooling rates on solidification and microstructure of rapidly solidified Mg₅₇Zn₃₇Y₆ quasicrystal alloy

Abstract

The influence of cooling rates on the solidification and microstructure of rapidly solidified quasicrystal alloys with a nominal compositions of Mg 57 Zn 37 Y 6 (at.%) prepared by melt spinning method was investigated. The microstructure, phase constitution, phase transition, and phase structure of the alloys were examined by means of scanning electron microscopy, x-ray diffraction, energy dispersive spectrometer, differential scanning calorimetry, and transmission electron microscopy. The results show that rapid solidification refines and homogenizes the microstructure of Mg 57 Zn 37 Y 6 alloys, compared to the conventionally-cast master alloy. With the increasing cooling rate of rapid solidification, the thickness of the ribbon decreases greatly and a larger amount of I-phase can be formed. a-Mg, MgZn, and icosahedral phases are found in the as-cast alloy, but the MgZn phase is absent from rapidly solidified alloys. The I-phase in both as-cast and rapidly solidified alloys can precipitate directly from the melt during the solidification process. A higher cooling rate can lead to a large degree of supercooling, resulting in a decreased phase transition temperature and a large number of icosahedral short-range orders (ISROs). ISROs can act as templates in liquid and promote the nucleation of I-phase.

Recent developments on fabrication of Al‐matrix composites reinforced with quasicrystals: From metastable to conventional processing

“…Most of these quasicrystals were discovered in the early 1990s by Inoue, Tsai and collaborators. In addition to Al-based systems, other important metallic systems forming quasicrystals are worth mentioning, such as Mg-based [17,18,19,20], Ti-based [21,22], and Cd-based [23,24].…”

Recent developments on fabrication of Al-matrix composites reinforced with quasicrystals: From metastable to conventional processing

“…Most of these quasicrystals were discovered in the early 1990s by Inoue, Tsai and collaborators. In addition to Al-based systems, other important metallic systems forming quasicrystals are worth mentioning, such as Mg-based [17,18,19,20], Ti-based [21,22], and Cd-based [23,24].…”

Microstructure and Indentation Properties of Single-Roll and Twin-Roll Casting of a Quasicrystal-Forming Al-Mn-Cu-Be Alloy

“…Generally, they are hard and brittle at room temperature. They can enormously enhance the mechanical properties when incorporated into a ductile metallic matrix [2][3][4][5]. Aluminium quasicrystal-strengthened alloys possess a periodic aluminium-rich matrix with a dispersed quasicrystalline phase [6,7].…”