Microstructural Analysis of Amorphous and Nanocrystalline Fe73.5-xCrxNb3Cu1Si13.5B9 Alloy by XRD Analysis

This thesis is based on the experimental investigation of the effect of grain size of Fe73.5-xCrxNb3Cu1Si13.5B9 [x = 7, 9, 10 & 12.5] alloys in the amorphous and annealed states. The samples are initially prepared in the amorphous state in the form of thin ribbons by rapid quenching technique at wheel speed of 25m/s in an Ar atmosphere. The alloy has been annealed in a controlled way in the temperature range of 450 - 800oC for 30 minutes. Amorphosity of the ribbon and nanocryatalline state was evaluated by XRD. In the optimized annealing condition the grain size has been obtained in the range of 11 - 30 nm. The primary crystallization phase shifts to higher annealed temperature with Cr content implying the enhancement of thermal stability of the amorphous alloys against crystallization due to increasing amount of Cr. The average grain size of the α-Fe (Si) phase, almost same under the identical annealing condition as the higher content Cr is increased. The peak shifts indicate the change of the values of Si-content of nanograins and therefore, the change of the values of lattice parameter of nanograins.