Effect Of Technical Parameters On Compositions,Nanostructures And Mechanical Properties Of Bulk Nanocrystalline Fe₃Al Materials Prepared By Aluminothermic Reaction

In this thesis, the recent development of Fe-Al intermetallics,bulk nanocrystalline materials and aluminothermic reaction is reviewed. The chemical composition,grain size and mechanical properties of bulk nanocrystalline Fe₃Al materials prepared by aluminothermic reaction in the different technical parameters are studied by means of experiment.The rules of effect of the different technical parameters on nanostructure and mechanical properties of the bulk nanocrystalline Fe₃Al materials are summed up.The main conclusions are given in the following.1. With the substrate's thickness increasing, grain size of bulk nanocrystalline Fe₃Al materials increased, bending strength,yield strength and hardness decreased. The thinner substrate is, the better mechanical properties materials have.2. With the qualities of reactant increasing, the amount of amorphous phase in bulk nanocrystalline Fe₃Al materials decreased, the average grain size of materials increased and a few of micron grains appeard in parts of areas. Bending strength,yield strength and hardness decreased with the qualities of reactant increasing. When the weight of reactant is light, materials have good mechanical properties.3. With the qualities of igniter increasing, the amount of amorphous phase in bulk nanocrystalline Fe₃Al materials decreased, the average grain size of materials increased and bending strength,yield strength and hardness decreased. According to the experimental results, as long as we can trigger aluminothermic reaction, the less igniter's quality is, the better mechanical properties materials have.4. The effect of diluter on the amount of every phase in materials is not remarkable. With the qualities of diluter increasing, the average grain size of materials and yield strength and hardness decreased.The existence of diluter make materials mechanical properties declined.5. With the argon pressure increasing, the composites and amounts of phases in materials are relatively stable,the average grain size of materials decreased and bending strength,yield strength and hardness increased. When argon pressure is larger, materials have good mechanical properties.6. The effect of milling time on nanostructure and mechanical properties of the bulk nanocrystalline Fe₃Al materials is not remarkable.When milling time is 8 h, bulk nanocrystalline Fe₃Al materials have the better overall properties. 7. The effect of molding pressure on the composites and amounts of phases in materials is not remarkable. With the molding pressure increasing, the average grain size of materials is stable, bending strength,yield strength and hardness of materials increased.The result shows that increasing molding pressure can improve materials mechanical properties.8. After annealing experiments found that when the annealing temperature has beenincreased to 1200℃, the average grain size of samples was basically stable.It shows that materials has good thermal stability.