Flash Joule heating for ductilization of metallic glasses.

I V Okulov,J Eckert,I V Soldatov,K Edström,M F Sarmanova,T Gemming,I Kaban

doi:10.1038/ncomms8932

Abstract

Metallic glasses (MGs) inherit their amorphous structure from the liquid state, which predetermines their ability to withstand high loads approaching the theoretical limit. However, the absence of slip systems makes them very sensitive to the type of loading and extremely brittle in tension. The latter can be improved by precipitation of ductile crystals, which suppress a catastrophic propagation of shear bands in a glassy matrix. Here we report a novel approach to obtain MG-matrix composites with tensile ductility by flash Joule heating applied to Cu47.5Zr47.5Al5 (at.%) metallic glass. This homogeneous, volumetric and controllable rapid heat treatment allows achieving uniformly distributed metastable B2 CuZr crystals in the glassy matrix. It results in a significant tensile strain of 6.8±0.5%. Moreover, optimized adjustment of the heat-treatment conditions enables tuning of microstructure to achieve desired mechanical properties.

Highlights

Metallic glasses (MGs) inherit their amorphous structure from the liquid state, which predetermines their ability to withstand high loads approaching the theoretical limit
The problem of drastic strain softening can be solved by precipitation of crystals, which tend to undergo a martensitic transformation on deformation, for example, the B2 CuZr phase in the CuZr system[4]
The metallic glass-matrix composites with B2 CuZr crystals/precipitates were obtained only by rapid quenching of the melt[16,17]

Summary

Results

Heat treatment of Cu47.5Zr47.5Al5 MGs. Up to date, the metallic glass-matrix composites with B2 CuZr crystals/precipitates were obtained only by rapid quenching of the melt[16,17]. The metallic glass-matrix composites with B2 CuZr crystals/precipitates were obtained only by rapid quenching of the melt[16,17] Fast and adjusted cooling on solidification promotes partial crystallization of the undercooled melt into B2 CuZr and prevents its decomposition into the low-temperature Cu10Zr7 and CuZr2 equilibrium phases (LTEPs)[18].

CuZr h1 h2

CuZr Cu10Zr7

Cu10Zr7

Discussion

Methods