Periodic Reporting for period 1 - PSMGDPP (Phase Separation in Metallic Glasses: Design, Phase Stability and Properties)
Reporting period: 2023-06-01 to 2025-05-31
The study of phase-separated metallic glasses (MGs) is motivated by both scientific curiosity and their potential practical applications. They offer insights into the behavior of disordered materials and open new avenues for designing advanced materials with tailored properties. Phase-separated MGs exhibit unique structural and physical characteristics that distinguish them from monolithic MGs. Moreover, they offer a unique opportunity to design composites or alloys with hierarchical microstructures across different length scales. Many efforts have been undertaken to understand the origin of phase separation in MGs; yet the understanding of the mechanism remains insufficient.
The main disadvantage of monolithic MGs utilized in biomedical applications is their poor global room temperature plasticity and the limited availability due to the presence of elements with high toxicity. Thus, it is important to develop new phase-separated MG systems that not only can improve the mechanical performance but also provide candidates for biomedical applications to acquire desirable combination of properties.
This project aims to synthesize new MGs by proper alloying addition, aiming to understand the genesis of phase separation. The effect of alloying addition on phase separation and properties will be investigated. Such studies will help to understand the structure (microstructure)-property co-relations in these alloy systems. The results of these investigations will be used as a guideline to modify the synthesis process to accomplish the main objectives, namely to obtain materials with desired properties. Novel dual-phase MGs will be designed with suitable mechanical properties for biomedical applications. In addition, we will explore the possibility of fabricating nano-porous network structure in phase separating MGs, which has the potential for various engineering applications. It is believed that this research will bring a significant impact for Europe to have a leading position in science, and for the researcher to have an excellent career development.
The main disadvantage of monolithic MGs utilized in biomedical applications is their poor global room temperature plasticity and the limited availability due to the presence of elements with high toxicity. Thus, it is important to develop new phase-separated MG systems that not only can improve the mechanical performance but also provide candidates for biomedical applications to acquire desirable combination of properties.
This project aims to synthesize new MGs by proper alloying addition, aiming to understand the genesis of phase separation. The effect of alloying addition on phase separation and properties will be investigated. Such studies will help to understand the structure (microstructure)-property co-relations in these alloy systems. The results of these investigations will be used as a guideline to modify the synthesis process to accomplish the main objectives, namely to obtain materials with desired properties. Novel dual-phase MGs will be designed with suitable mechanical properties for biomedical applications. In addition, we will explore the possibility of fabricating nano-porous network structure in phase separating MGs, which has the potential for various engineering applications. It is believed that this research will bring a significant impact for Europe to have a leading position in science, and for the researcher to have an excellent career development.
A significant achievement of the PSMGDPP project is the successful design of phase-separated Zr (Y)-Al-Fe MGs by alloying addition with Y, a first in this field. The microstructure of phase-separated nano-amorphous domains has been confirmed by sophisticated experimental characterization techniques including transmission electron microscopy (TEM) and atom probe tomography (APT). The alloys exhibit a typical liquid phase separation-induced two-glassy phase (Zr-rich and Y-rich) structure with droplet-like microstructures (nano-amorphous domains). APT investigations confirm the presence of nanometer-sized Y-enriched clusters in the alloys. Microstructure analysis through TEM and APT revealed that the size of nano-amorphous domains increases with increasing Y addition. A key finding of our investigation is the low Young’s modulus in the range of ~81–91 GPa for these phase-separated MGs, attributed to the presence of mechanically soft, Y-enriched glassy regions. Their modulus is lower than that of Co-Cr-Mo, 316L SS and Ti-6Al-4V commercial implant alloys. The in-situ TEM tensile deformation test shows an improvement in plastic behavior, with the plastic strain nearly doubling, clearly indicating enhanced ductility in the phase-separated MGs. The cytocompatibility evaluation of the MG ribbons shows a higher metabolic activity of HGF cells on the surface of samples. Thus, the two glassy-phase Zr-based MGs exhibit suitable mechanical properties and biocompatibility, making them strong contenders for implant applications. For the fabrication of nano-porous MGs, corrosion results show that adding Y, which promotes phase separation, leads to limited passivation and increased electrochemical reactivity. Notably, the corrosion process is accompanied by a significant increase in surface roughness, as well as the development of porosity.
During the course of our investigation on Ce-Ni-Al (Ga) MGs, a new MG composition, Ce60Ni25Ga15, was observed by complete substitution of Al with Ga. The expansion of the supercooled liquid region provides strong evidence for the better glass-forming ability of the Ce60Ni25Ga15 composition, indicating its potential for enhanced stability and processing characteristics. The Ce-Ni-Al (Ga) MGs do not exhibit phase separation, differing from our earlier work on Ce–Al (Ga) MGs, where phase separation was observed due to changes in the electronic structure of Ce atoms. Deformation in Ce-Ni-Al (Ga) MGs occurs by the evolution of shear bands. The significant improvement in the micro-hardness has been observed by alloying addition with Ga, suggesting an increased resistance to deformation. The magnetic properties of the alloys exhibit paramagnetic characteristics, with magnetization slightly decreasing as Ga content increases. Altogether, this study contributes to the understanding of the microstructural characteristics and the nature of the deformation mechanism in MGs.
During the course of our investigation on Ce-Ni-Al (Ga) MGs, a new MG composition, Ce60Ni25Ga15, was observed by complete substitution of Al with Ga. The expansion of the supercooled liquid region provides strong evidence for the better glass-forming ability of the Ce60Ni25Ga15 composition, indicating its potential for enhanced stability and processing characteristics. The Ce-Ni-Al (Ga) MGs do not exhibit phase separation, differing from our earlier work on Ce–Al (Ga) MGs, where phase separation was observed due to changes in the electronic structure of Ce atoms. Deformation in Ce-Ni-Al (Ga) MGs occurs by the evolution of shear bands. The significant improvement in the micro-hardness has been observed by alloying addition with Ga, suggesting an increased resistance to deformation. The magnetic properties of the alloys exhibit paramagnetic characteristics, with magnetization slightly decreasing as Ga content increases. Altogether, this study contributes to the understanding of the microstructural characteristics and the nature of the deformation mechanism in MGs.
The findings obtained in this study extend the current understanding of phase-separated MGs, particularly with regard to the role of alloying additions in influencing their microstructure and properties. The mechanical properties of MGs can be improved by phase separation in the form of nano-amorphous domains. By employing this nanostructured design approach, amorphous alloys can achieve a remarkable balance of strength and ductility, effectively overcoming the inherent brittleness typically seen in monolithic amorphous materials at room temperature. This strategy not only improves the overall mechanical performance but also opens up new possibilities for using amorphous alloys in applications requiring both high strength and toughness. Moreover, the interdisciplinary outcomes of this work—encompassing alloy design, advanced microscopy, and mechanical characterization—offer new insights into the thermodynamics and kinetics of phase separation in multicomponent amorphous systems. These results provide a deeper understanding of the structure (microstructure)–property correlations governing the behavior of phase-separated MGs and establish a foundation for the design of next-generation MGs with enhanced functional and mechanical capabilities.