Abstract
The critical cooling rate necessary for glass formation via melt solidification poses inherent constraints on sample size using conventional casting techniques. This drawback can be overcome by pressure-assisted sintering of metallic glass powders at temperatures above the glass transition, where the material shows viscous-flow behavior. Partial crystallization during sintering usually exacerbates the inherent brittleness of metallic glasses and thus needs to be avoided. In order to achieve high density of the bulk specimens while avoiding (or minimizing) crystallization, the optimal combination between low viscosity and long incubation time for crystallization must be identified. Here, by carefully selecting the time–temperature window for powder consolidation, we synthesized highly dense Zr48Cu36Ag8Al8 bulk metallic glass (BMG) with mechanical properties comparable with its cast counterpart. The larger ZrCu-based BMG specimens fabricated in this work could then be post-processed by flash-annealing, offering the possibility to fabricate monolithic metallic glasses and glass–matrix composites with enhanced room-temperature plastic deformation.
Highlights
Bulk metallic glasses (BMGs) are materials with liquid-like structure [1] exhibiting high strength and hardness, large strain elastic limit (~2%), and good wear and corrosion resistance [2], which represent an attractive combination of properties for applications in the field of structural materials
The results indicate that highly dense BMG specimens with mechanical properties comparable with the corresponding material prepared by casting can be synthesized by using powder metallurgy
We further explore the process of consolidation of amorphous powders by analyzing the effectiveness of hot pressing for the synthesis of Zr48 Cu36 Al8 Ag8 BMGs
Summary
Bulk metallic glasses (BMGs) are materials with liquid-like structure [1] exhibiting high strength and hardness, large strain elastic limit (~2%), and good wear and corrosion resistance [2], which represent an attractive combination of properties for applications in the field of structural materials. The necessity for rapid heat extraction and the corresponding high cooling rates essential for glass formation by melt solidification set an inherent limit to the achievable dimensions of bulk metallic glass specimens [3]. This aspect is explained, which shows a schematic continuous cooling transformation (CCT). Solidification of larger specimens will lead to partial or full crystallization. Such crystallization usually occurs with the formation of brittle intermetallic phases, which further reduces the limited plastic deformation of metallic glasses at room temperature [6]. The restriction in sample size obviously limits the potential applications of BMGs
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