Correlation between medium-range order structure and glass-forming ability for Al-based metallic glasses

Abstract

To clarify the correlation of medium-range order (MRO) structure with glass forming ability (GFA) of Al-based metallic glasses, Al 86 Ni 14-a Y a (a ¼ 2$9 at. %) metallic glasses were analyzed by x-ray diffraction in detail and further verified by synchrotron high-energy x-ray diffraction. The prepeak that reflects the MRO structural evolution was found to be much sensitive to alloy composition. We have proposed an icosahedral supercluster MRO structure model in Al-TM (transition metal)-RE (rare earth metal) system, which consists of 12 RE(TM)-centered clusters on the vertex of icosahedral supercluster, one RE(TM)-centered clusters in the center, and TM(RE) atoms located at RE(TM)-centered cluster tetrahedral interstices in the icosahedral supercluster. It was indicated that the MRO structural stability mainly depends on the interaction of efficient dense packing and electrochemical potential equalization principle. The Al 86 Ni 9 Y(La) 5 alloys present good GFA due to the combination of the two structural factors. V

Designing aluminum-rich bulk metallic glasses via electronic-structure-guided microalloying

“…2b). The prepeak in the XRD curves reflects the medium range correlation [9], which appears to vary with the Co addition.…”

“…A large number of studies [8][9][10][11] have aimed at overcoming this bottleneck problem of low glass-forming ability (GFA), only to discover that the various empirical guidelines [12][13][14] learnt from prior experience with other BMG alloy systems are of limited use in Al-rich alloys. Generally speaking, minor alloying addition (often dubbed as "micro-alloying" [15]) is left as the primary approach to elevate the GFA [7,[16][17][18][19][20][21][22][23][24].…”

Evaluation of glass formation and critical casting diameter in Al-based metallic glasses

“…The size limitation of Al-based metallic glasses has hindered its further development in many relevant areas, such as the optional design of microstructure [9,11], the investigation of corrosion-resisting properties with large scale metallic coatings [4] and the mechanical properties investigation of BMGs with selective laser melting (SLM) technique [12][13][14] etc. In order to design larger Al-based BMG to fulfill its potential application, many methods, e.g., theoretical models [6,7,15,16] and empirical criterions [1,8], have been proposed. Unfortunately, solidification process, another key factor closely related to sample size, has rarely been analyzed in Al-based BMGs in previous researches.…”

Recent Topics on the Structure and Crystallization of Al-based Glassy Alloys

“…Based on the EAPCC, Wu et al 141 further proposed an icosahedral supercluster MRO structure model to describe the connection between the clusters. A supercluster consists of 12 RE-centered clusters or 12 TM-centered clusters on the vertex of the supercluster, in which the centered TM and RE are surrounded only by Al atoms.…”