Microstructure and magnetocaloric effects in partially amorphous Gd55Co15Al30-xSix alloys

Highlights: → The primary crystalline phase of the metallic glasses is identified to be Gd2Al. → Phase separation is observed in the system with negative heat of mixing. → Relationship between the microstructure and MCE of Gd-based BMG composite. - Abstract: In order to clarify the phase components and further improve the glass-forming ability of Gd55Co15Al30 alloy, substitution of Al with Si was adopted. Although the X-ray powder diffraction experiment indicated an amorphous structure of the Gd55Co15Al30-xSix (x = 1, 2, 3) alloys, precipitation of crystalline Gd2Al phase was evident from the energy-dispersive spectroscopy, selected-area diffraction, and magnetization measurements. The magnetocaloric effect of Si substituted alloys is lower than that of Gd52.5Co16.5Al31 alloy with a similar composition and full amorphous structure, which is ascribed to the presence of antiferromagnetic Gd2Al phase whose magnetic entropy change is lower.