Effect of Annealing on Hardness and the Modulus of Elasticity in Bulk Nanocrystalline Nickel (original) (raw)
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Materials Science and Engineering: A, 2013
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Journal of the Electrochemical Society, 2013
Nickel-iron alloy coatings were produced by electrodeposition from an additive free electrolyte, at room temperature and current density in the range of 1 to 5 A dm −2 , with Fe content up to 75 wt%. The structure and mechanical properties of the electrodeposited alloys are reported in the present work and analyzed focusing on structure-property relationships. In particular, the influence of the hydrogen evolution reaction is highlighted as a process factor affecting alloy phase structure, notably the composition limit of the γ-phase field. The variations of the mechanical properties with alloy composition are analyzed in the light of the concurrent modifications in phase structure and crystal size of the alloys. In particular, an assessment of the different factors influencing the hardness of γ phase alloys is proposed. Solid solution effects contribute significantly to the strength of γ phase alloys over a wide composition range, approximately from 5 to 25%, though a complex interplay between solid solution and Hall-Petch strengthening needs to be envisaged to account for the variations in hardness with composition over this range. Moreover, it is emphasized that with decreasing grain size, the increasing level of internal stresses and decreasing stiffness engender significant softening in nanocrystalline γ phase alloys with Fe content exceeding about 25%.
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Materials Testing, 2020
Nanocrystalline nickel-iron layers are produced electrochemically on copper discs by varying the current density and then annealed in a vacuum furnace at a temperature range between 200 and 800 °C. Grain size, iron content, texture and microstrain of the microstructure are primarily characterized by X-ray diffraction (XRD). Instrumented indentation tests and microbending tests for mechanical characterization are carried out. The iron contents of the investigated layers are 5.7, 8.8, 13.5 and 17.7 wt.-%. By varying the annealing temperature, the reduction of the microstrains is initiated at 200 °C and ends at a temperature of about 280 °C. Primary recrystallization starts slightly higher at 220 °C and is completed at 300 °C. With higher iron content, the indicated temperatures shift to slightly higher values. Indentation modulus, Young's modulus, indentation hardness and strength change considerably after the annealing treatment. Fracture strain at the edge, as a measure of ducti...