Study Of Hot Pressing On The Microstructures And Mechanical Properties Of Bulk Nanocrystalline Fe₃Al Based Alloys Containing Several Elements

In this thesis, the recent development of Fe-Al intermetallics. Bulk nanocrystalline Fe3Al materials made by aluminothermic reaction were reviewed. Effect of the hot pressing temperatures, times and pressures on the microstructure and mechanical properties of bulk nanocrystalline Fe3Al with 10 wt.% Mn,10 wt. % Cr and 10 wt.% Ni elements are studied. The rules of hot pressing parameters on nanostructure and plastic deformation of the bulk nanocrystalline Fe3Al materials were summed up. The possibility of size increase of nanostructure materials by hot pressing was explored. The main conclusions are given in the following.1. Bulk nanocrystalline Fe3Al materials containing different elements show different plastic deformation in hot pressing. The plastic deformation of materials were increased with hot pressing temperature rising. The bulk nanocrystalline Fe3Al materials with 10 wt.% Mn have a better plasticity at 600℃,800℃and 1000℃. But the bulk nanocrystalline Fe3Al materials with 10 wt.% Cr have a good plasticity only at 600℃and exhibited brittle fracture at 800℃and 1000℃. The bulk nanocrystalline Fe3Al materials withlO wt.% Ni has a good plasticity at 800℃and 1000℃and shows brittle fracture at 600℃.2. Bulk nanocrystalline Fe3Al materials with 10 wt.% Mn and 10 wt.% Cr mainly consist of Fe3Al phases with disorder bcc crystal structure before and after hot pressing. But the bulk nanocrystalline Fe3Al materials withlO wt.% Ni mainly consist of Fe3Al phases with disorder bcc crystal structure before hot pressing and changed to ordered DO3 crystal structure after hot pressing.3. Grain sizes of bulk nanocrystalline Fe3Al materials with different elements were increased with hot pressing temperatures increasing. The hardness of bulk nanocrystalline Fe3Al materials with 10 wt.% Mn and 10 wt.% Cr were increased after hot pressing, the hardness of Fe3Al materials with 10 wt.% Ni was decreased after hot pressing. Relationship of the hardness of the nanocrystalline Fe3Al materials with 10 wt.% Mn with grain size after hot pressing is contrary to the Hall-Petch relation.4. Plastic deformation of bulk nanocrystalline Fe3Al materials with different elements were increased with hot pressing times increasing. Grain sizes and hardness of bulk nanocrystalline Fe3Al materials with 10 wt.% Mn were decreased with hot pressing times increasing. Grain sizes of bulk nanocrystalline Fe3Al materials with 10 wt.% Cr and 10 wt.% Ni were increased with hot pressing times increasing, but the hardness is changelessness. Relationship of the hardness of the nanocrystalline Fe3Al materials with 10 wt.% Mn with grain size after hot pressing is contrary to the Hall-Petch relation.5. Bulk nanocrystalline Fe3Al materials with 10 wt.% Mn and 10 wt.% Cr have a good plasticity at different hot pressing pressures. Plastic deformation of bulk nanocrystalline Fe3Al materials was increased with hot pressing pressures increasing. The grain sizes and hardness changes are little with hot pressing pressures increasing.6. Geometry of bulk nanocrystalline Fe3Al materials containing different elements after hot pressing can be increased.