Al-based amorphous alloys: Glass-forming ability, crystallization behavior and effects of minor alloying additions

Abstract

The main recent advances in Al-based amorphous alloys are discussed in three areas: crystallization behavior, glass-forming ability and minor alloying effects. First, as a brief introduction, the special features and structure-property relationships are presented for the Albased amorphous alloys. The different models for the nucleation behaviors, such as phase separation model and the quenched-in nuclei model, are compared and evaluated. In addition, an overview is given for the effects of minor alloying additions on glass-forming ability (GFA) and the crystallization behavior in terms of the reported structural, thermodynamic, kinetic factors.

Al‐Based Amorphous Metallic Plastics

“…For MGs, the TTT diagram is usually measured by the isothermal experiments. However, for the Al‐based MGs, there is a primary nucleation peak for Al nanocrystals and this signal from the primary nucleation is very weak in the isothermal DSC trace so that there is no obvious peak that could be detected by normal DSC . However, by the Flash DSC with ultrafast heating rate, it is possible to precisely confirm the onset time of primary crystallization for Al‐based MGs .…”

High strength nanostructured Al-based alloys through optimized processing of rapidly quenched amorphous precursors

“…The decrease of the Avrami exponent ( n ) from 3.41 ± 0.3 to 2.98 ± 0.3 with increasing annealing temperature can be explained from the phase formation of α-Al. When fcc Al nanocrystals are formed from the amorphous phase, they reject solute elements such as Ni, Co and Dy into the residual amorphous matrix 35 . This reduces the driving force for the formation of additional fcc Al and accumulates Dy around the α-Al precipitates, thus impeding diffusion of the elements required for further growth of the nanocrystals.…”

Thermally induced phase transformations of Al93Fe4Nb3 and Al90Fe7Nb3 quenched alloys

“…The alloy's properties notably depend on the synthesis methods (plasma spraying, ion irradiation, laser treatment, melt-spinning). The using of controllable rapid quenching allows obtaining the alloys with complex amorphous-nanocrystalline structure with the possibility of metastable phases (supersaturated solid solution and quasicrystals) formation [9]. In particular, during a quenching of binary Al-Fe alloys the formation of few metastable Al-based phases structurally related to icosahedral symmetry was observed [10].…”