TY - JOUR

T1 - Cryo-Casting for Controlled Decomposition of Cu-Zr-Al Bulk Metallic Glass into Nanomaterials

T2 - Implications for Design Optimization

AU - Sarac, Baran

AU - Kim, Jeong Tae

AU - Ivanov, Yurii P.

AU - Soprunyuk, Viktor

AU - Ketov, Sergey V.

AU - Schranz, Wilfried

AU - Hong, Sung Hwan

AU - Kim, Ki Buem

AU - Greer, A. Lindsay

AU - Eckert, Jürgen

N1 - Publisher Copyright: © 2021 American Chemical Society.

PY - 2021/7/19

Y1 - 2021/7/19

N2 - Cryo-cooled copper-mold suction casting reveals an unexpected phase separation (PS) in Cu46Zr46Al8 bulk metallic glass (BMG) by controlled atomic diffusion. The decomposed alloy cryo-cast to 193 K exhibits a remarkably lower free volume than the alloy cast to room temperature manifested by dilatometry. An unusual endotherm after the onset of relaxation registered by differential scanning calorimetry and compositional homogenization occurring on long time scales upon post-heat treatment even above the glass-transition temperature confirm the stability of the decomposed state against crystallization. As revealed by scanning transmission electron microscopy and energy-dispersive X-ray analysis, single-stage PS (cryo-cast to 193 K) results in distinct and evenly dispersed nanoscale Cu- and Zr-rich regions, whereas two-stage PS (cast to 298 K) involves further decomposition of existing Cu- and Zr-rich regions on a finer scale. Notably, PS accounts for macroscopic compressive plasticity at no expense of fracture strength. This study opens opportunities for the design optimization of homogeneously dispersed amorphous nanostructures of controllable size and composition in BMGs by single- or multistage decomposition through mold temperature control.

AB - Cryo-cooled copper-mold suction casting reveals an unexpected phase separation (PS) in Cu46Zr46Al8 bulk metallic glass (BMG) by controlled atomic diffusion. The decomposed alloy cryo-cast to 193 K exhibits a remarkably lower free volume than the alloy cast to room temperature manifested by dilatometry. An unusual endotherm after the onset of relaxation registered by differential scanning calorimetry and compositional homogenization occurring on long time scales upon post-heat treatment even above the glass-transition temperature confirm the stability of the decomposed state against crystallization. As revealed by scanning transmission electron microscopy and energy-dispersive X-ray analysis, single-stage PS (cryo-cast to 193 K) results in distinct and evenly dispersed nanoscale Cu- and Zr-rich regions, whereas two-stage PS (cast to 298 K) involves further decomposition of existing Cu- and Zr-rich regions on a finer scale. Notably, PS accounts for macroscopic compressive plasticity at no expense of fracture strength. This study opens opportunities for the design optimization of homogeneously dispersed amorphous nanostructures of controllable size and composition in BMGs by single- or multistage decomposition through mold temperature control.

KW - cryo-casting

KW - electron microscopy

KW - heat treatment

KW - metallic glass

KW - nanostructures

KW - phase separation

KW - structural relaxation

UR - http://www.scopus.com/inward/record.url?scp=85111584696&partnerID=8YFLogxK

U2 - 10.1021/acsanm.1c01055

DO - 10.1021/acsanm.1c01055

M3 - Article

AN - SCOPUS:85111584696

VL - 4.2021

SP - 7771

EP - 7780

JO - ACS Applied Nano Materials

JF - ACS Applied Nano Materials

SN - 2574-0970

IS - 8

ER -