Effect of Continuous Wave Laser Irradiation on Structural Relaxation and Mechanical Properties of Fe-si-b Amorphous Ribbon

Abstract

The thermal treatment of amorphous alloys results in change in their properties due to structural relaxation and crystallization. Laser irradiation permits very high control in site-specific thermal treatment of material. The present study was aimed at investigating structural relaxation and resulting change in mechanical properties of Fe-Si-B amorphous ribbon under laser irradiation. The alloy was irradiated by a continuous wave Nd:YAG laser. Three different scanning speeds (500, 600, and 700 mm/s) were chosen with constant laser power at 100 W. No crystallization was observed from microstructural and XRD analyses. Thermal simulation revealed that the maximum temperature was 357 �C, which was below crystallization temperature of the alloy. DSC analysis revealed structural relaxation for all the scanning speeds. Thermal embrittlement, microhardness and structural distortion were measured and related with relaxation and laser scanning speed. Reduction in fracture stress and strain were more than 50% for 500 mm/s. Microhardness was increased by 4-5%. Structural distortion was enhanced at lower laser scanning speed. Thermal stress was found to be tensile in nature at the middle of the irradiated area and as high as 350 MPa. Since there was no other than thermal load acting on the material during irradiation, it seems that the thermal stress was responsible for the structural distortion.