F Javaherian - aNanomaterial Group, Department of Metallurgy and Materials Engineering, Iran University of Science &Technology (IUST), Tehran, Iran
A Beitollahi - aNanomaterial Group, Department of Metallurgy and Materials Engineering, Iran University of Science & Technology (IUST), Tehran, Iran
F Shahri - bFaculty of Engineering and High-Tech., Iran University of Industries and Mines (IUIM), Tehran, Iran
H Aliakbarzadeh - Maham Institute of Science and Technology

In this work, we have studied the effect of rapid thermal annealing on structure and magnetoimpedance effects and magnetic properties of rapidly quenched Fe71Si13.5B9Nb3Cu1Al1.5Ge1 alloys prepared by single roller melt spinning process. The nanocrystallization process was carried out by the heat-treatment of as-spun ribbons by joul heating method at constant current of 0.9 A, 10,20,30 and 60 seconds in a vaccum furnace. X-ray differaction (XRD), differential scanning calorimetry (DSC) and magnetoimpedance (MI) measurmenets were conducted on the asquenched and heat-treated alloys to investigate the structural,thermal and magnetic properties. The removal of stress and the set up of nanocrystallization during the dc-joul heating process gave rise to a higher of magnetoimpedance ratio (MIR%) as confirmed by our XRD results. However increase in applied time and current during the dc-joule heating treatment has led to grain growth and also establishment of Fe-B hard magnetic phase. GMI amount, decreased by grain growth and the presence of hard magnetic Fe-B phase. Finally, relationship between structure and magnetic properties of specimen has been investigated in various samples.

Nanostructured materials, Finemet alloy, Magnetoimpedance, Softmagnetic properties