Peculiarities of the Low Magnetostrictive Amorphous Ribbons Crystallization Under Laser Heating

Abstract

The crystallization of the low magnetostrictive amorphous metallic alloy Co 68 Fe 4 Cr 4 Si 13 B 11 obtained by melt-spinning after bulk annealing (BA) and surface laser heating (LH) has been investigated by X-ray powder diffraction method. As shown, both at volume and laser heating the first phase to crystallize was cobalt. Increase in BA temperature led to the formation and decomposition of a great number of metastable phases. Stable phases Co and (Co,Si) 2 B appeared as final products of crystallization. The number of simultaneously coexisting crystalline phases was smaller after LH. The final products of crystallization under LH in the most permissible regimes (those not leading to the sample decay) were the phases Co, (Co,Si) 3 B and (Co,Si) 2 B (under pulse LH) and Co, (Co,Si)B and (Co,Si) 2 B (under continuous CO 2 LH). A sandwich structure was observed in the cross section of the ribbon after some regimes of LH. The ribbon was crystalline at the side of the treated surface and amorphous at the side of the opposite surface. X-ray analysis revealed that the high rates of laser heating and cooling lead to a change in crystallization reaction: from the primary crystallization observed at BA to the eutectic crystallization at LH.