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Bulk metallic glasses (BMGs) exhibit superior mechanical properties combining high mechanical strength with a higher elastic strain limit in comparison with crystalline metals [1]. In addition, they show excellent wear properties and corrosion resistance due to the lack of grain boundaries. The absence of the conventional plastic flow carriers and dislocations inhibits BMGs from plastic deformation. This unconventional modality of deformation through highly localized shear bands raised great interest in these materials. However, macroscopic brittleness leads to catastrophic failure when deforming beyond the elastic strain limit [2]. For the improvement of BMG formation and processing, a thorough understanding of the crystallization kinetics is required as well as refined models of crystal nucleation and growth. Crystallization kinetics trigger heterogeneous nucleation such as strain induction, reaction with the atmosphere, materials viscosity and gravity.
The solidification of Zr- and Pd- based BMGs under gravity and micro-gravity conditions [3,4] has been studied by means of XRD and total scattering experiments after processing. We obtained results on atomic pair-pair correlation functions for the local structure of the system allowing us to estimate the bond length, the average coordination number and the free volume, a parameter that correlates the structure and BMGs properties such as the glass-forming ability and mechanical properties [5]. Partially crystallised systems have also been investigated. We correlated our results with complementary tomographic scans, allowing the pore structures to be visualised. Thus providing a multi-scale physical picture of the BMG system.
[1] W.H. Wang et al., Materials Science and Engineering: Reports, 44, 45-89, (2004).
[2] M. M. Trexler et al., Progress in Materials Science, Volume 55, Issue 8, (2010).
[3] M. Mohr et al., NPJ Microgravity, 2019, 5(1), 4, 1-8, (2019).
[4] N. Sohrabi et al., Materials and Design 199 (2021) 109400.
[5] J. Tan et al., Appl. Phys. Lett. 98, 151906 (2011).
| Speaker Country | Schweiz |
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