Correlation between supercooled liquid region and crystallization behavior with alloy composition of La-Al-Cu metallic glasses

Abstract

Bulk metallic glasses (BMGs) with large supercooled liquid region are promising materials for superplastic forming. In this paper, we demonstrate a microstructure-based strategy to pinpoint the composition with the largest supercooled liquid region in La 86−x Al 14 Cu x (x=16 at%-20 at%) metallic glass system. By monitoring the changes in crystallization behavior of the glassy alloys with composition to search for the alloys exhibiting eutectic crystallization, the glassy alloys with the largest supercooled liquid region in the given alloy system can be found. The metallic glasses with Cu contents of 16 at%-19 at% exhibited two crystallization peaks, and the primary crystallization product was identified to be α-La by means of DSC, XRD and TEM. The increase in Cu content resulted in the decay of the primary crystallization peak and the increase in onset temperature of crystallization, leading to the enlargement of supercooled liquid region. By further suppressing the α-La primary crystallization with increasing Cu content up to 20 at%, the eutectic crystallization of α-La and LaCu 13 through one crystallization reaction occurred upon heating, where the largest supercooled liquid region of 65 K for La 66 Al 14 Cu 20 glassy alloy was located. This study indicats that, in a given glassy alloy system, a larger supercooled liquid region can be achieved by optimizing the alloy compositions to suppress the primary crystallization. bulk metallic glass, supercooled liquid region, crystallization PACS: 81.05.Kf, 81.10.Aj, 64.70.Pf

Oxidation Behavior of Zr-based Amorphous Alloys at 400˚- 450˚C in Air

“…This is related to the super cooled liquid area that is formed. Increased T g and T x due to increased heating rates accompanied by increased super cooled liquid areas (Q. C. Zhang, Pang, Li, & Zhang, 2011).…”

Effect of Friction Stir Processing on Hardness and Microstructure in La-Based Bulk Metallic Glass Composites

“…After all, it is the BMGCs who can basically meet the requirements of engineering applications, due to the fact that some BMGCs can not only exhibit the special mechanical, chemical and physical properties of single-phase bulk metallic glasses (BMGs), but also can overcome the brittleness problem of single-phase BMGs at room temperature. 5) The material used in this study is one of the best known glass formers in the La-based system, La 66 Al 14 Cu 20 , with very low glass transition temperature of 391 K and a large supercooled liquid region of 65 K. 6) A relatively wide operating window and a low working temperature are necessary for the FSP without auxiliary heating. FSP was conducted on a 2.5 mm thick La 66 Al 14 Cu 20 BMGCs plate.…”