Microstructure and mechanical properties of Fe-48(wt.%)Ni alloy processed by equal channel angular pressing
Résumé
The microstructure and mechanical properties of a Fe-48wt%Ni alloy in form of stacked sheets and bulk billet after severe plastic deformation using equal channel angular pressing (ECAP) were investigated. Samples were passed through a die with an inner angle of Φ = 90° and outer arc of curvature of ψ = 17° at room temperature. X-ray diffraction and Electron Backscatter Diffraction were used to evaluate phase transformation and microstructure before and after ECAP process. Heterogeneous structure was identified by the formation of shear bands during severe plastic deformation. The crystallite size decreased down to 30 nm. In order to characterize the mechanical properties, tensile tests were carried out. Results of mechanical tests showed a significant loss of ductility after ECAP compared to the initial material with an increase in tensile strength from 459 MPa to a maximum value of 676 MPa. This increase is accompanied by enhanced dislocation density (2.10 15 m-2) and was related to grain refinement. Moreover, the alloy has shown a decrease in elongation to failure to values of approximately 22%. The fracture surface morphology shows the formation of a specific dimple relief.
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