Effect Of Alloying Elements And Annealing On Properties Of Bulk Nanocrystalline Fe₃Al Materials Prepared By Aluminothermic Reaction

In this thesis, the properties and strengthening method of Fe-Al intermetallics and aluminothermic reaction is reviewed. The mechanical properties, magnetic properties, oxidation resistance and corrosion resistance of bulk nanocrystalline Fe3Al materials with different elements prepared by aluminothermic reaction are studied by means of experiment. The rules of effect of the different elements on properties of the bulk nanocrystalline Fe3Al materials are summed up. The main conclusions are given in the following.1. With the content of Cu increasing, grain size of bulk nanocrystalline FesAl materials containing 10 wt.% Ni increased first and then decreased. The grain size of material with 10 wt.% Ni,2wt.% Cu was the smallest and with the content of Cu increasing, the hardness increased first and then decreased. But the compressive yield strength of material decreased first and then increased with the content of Cu increasing.2. The addition of Si element to Fe3Al materials with one element Cr, Cu or Mn made the average grain size of the samples decreased and the hardness and mechanical properties of the samples increased significantly. After adding Si element, the compressive yield strength of material containing 10 wt.% Cr elements decreased about 150 MPa, but the compressive yield strength of materials containing 10 wt. % Mn elements and 5 wt.% Cu elements increased.3. After annealing, the bulk nanocrystalline Fe3Al material containing 5 wt.% Cu has good plasticity and its grain size increased a little, the average grain size of the bulk nanocrystalline Fe3Al material with 10 wt.% Ni increased with the annealing temperature increased and the hardness reached maximum at 800℃. After annealing, the material containing 15 wt.% Mo has good plasticity and its compressive yield strength increased significantly.4. With the substrate's thickness increasing, grain size of bulk nanocrystalline Fe3Al materials containing 10 wt.% Ni increased, hardness changed little. With the content of diluter increasing, the yield strength of materials decreased first and then increased. When the diluter is 20 wt.%, the average grain size of materials was the smallest.5. The effect of alloy elements on magnetic properties of nanocrystalline materials Fe3Al was significantly. Adding Cr or Mn elements made the magnetic properties of nanocrystalline Fe3Al decreased but adding 10 wt.% Ni made the material coercivity and residual magnetization decreased and saturation magnetization increased. The magnetic properties of materials with 10 wt.% Ni and 2 wt.% Cu was lower than that of Fe3Al materials with 10 wt.% Ni. The magnetic properties of nanocrystalline Fe3Al materials with 10 wt.% Ni by 1000℃heat treatment was far less than that without heat treatment.6. The uniform corrosion rate of nanocrystalline samples was much faster than the stainless steel samples. As adding the alloy elements, oxidation rate of Fe3Al samples increased and its oxidation resistance reduced. The average oxidation rate of bulk nanocrystalline Fe3Al based materials except that with 10 wt.% Mn are smaller than that of heat-resistant steel 310S.