Fe-based bulk metallic glass composites without any metalloid elements

• Published in: Acta materialia 2013-05, Vol.61 (9), p.3214-3223
• Main Authors: Gao, J.E., Chen, Z.P., Du, Q., Li, H.X., Wu, Y., Wang, H., Liu, X.J., Lu, Z.P.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bulk metallic glass; Exact sciences and technology; Glass matrix composites; Glass-forming ability; Metals. Metallurgy; Phase separation; Positive enthalpy of mixing
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2013.02.009

Glass-formation of Fe-based bulk metallic glasses (BMGs) and their composites is strongly dependent on their metalloid content. A good Fe-based glass former usually needs a metalloid content of ∼20at.% or above; however, the high content of the metalloids usually has side-effects on the performance of the alloys. In this paper, we developed a series of metalloid-free Fe-based BMG matrix composites with a diameter of more than 10mm in the Fe–Co–La–Ce–Al–Cu system. During cooling, phase separation took place, i.e. Fe-rich and Fe-depleted liquids formed. Upon subsequent cooling, the body-centered cubic (bcc)-Fe(Co, Al) solid solution and Ce(Fe, Co)2 intermetallic phase precipitated out of the Fe-rich liquid and the remaining Co–La–Ce–Al–Cu liquid was eventually vitrified to form the amorphous matrix. Due to elemental partitioning, it was found that, for a given Fe content, there exists an optimum compositional range for Co and Ce so that a large fraction of the glassy matrix can form. In addition, the final microstructure of the current composites was strongly dependent on the cooling rates applied: excessively fast cooling rates restricted the diffusion and precipitation of the Fe atoms, which reduced formation of the glassy matrix.