PSI - Issue 50

V.N. Kostin et al. / Procedia Structural Integrity 50 (2023) 147–150

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V.N. Kostin et al./ Structural Integrity Procedia 00 (2022) 000 – 000

Nickel is widely used in modern technology. Most of the nickel is used to obtain alloys with other metals (Fe, Cr, Cu, etc.), which are distinguished by high mechanical, anticorrosive, magnetic or electrical and thermoelectric properties. The works of Pollock et al., 2006 and Thakur et al., 2015 consider special nickel-based alloys, which are an unusual class of metallic materials with an exceptional combination of high-temperature strength, toughness, and resistance to destruction in aggressive or oxidizing environments, as well as their chemical composition and microstructure. These alloys are widely used as functional heat-shielding coatings in aircraft and power turbines (Furrer et al., 1999; Kutepov et al., 2022), rocket engines, petrochemical plants, nuclear power, marine equipment to protect products subjected to intense temperature and force effects. Nickel-based alloys are also used in dentistry (Wylie et al., 2007). However, nickel-based specialty alloys are among the most difficult materials to machine. During processing, the interaction between the tool and the workpiece causes strong plastic deformation in the local area of the workpiece and intense friction at the tool – workpiece interface. The resulting high cutting temperature, combined with severe hardening, leads to several disadvantages, such as excessive tool wear, frequent tool changes, short tool life, low productivity, high power consumption, etc. (Zhu et al., 2013). A significant amount of nickel is used to produce alkaline batteries and anti-corrosion coatings. Malleable nickel in its pure form is used for the manufacture of sheets, pipes, etc. It is also used in the chemical industry for the manufacture of special chemical equipment and as a catalyst for many chemical processes. The aim of this work is an experimental study and analysis of the effect of plastic deformation and subsequent annealing on the complex of magnetic characteristics of nickel. This work is carried out in the framework of research of the stress-deformed state of Fe-Ni alloys (Kostin et al., 2022). 2. Samples and equipment For the study, a group of ten samples was prepared, which were made from commercially pure nickel. The workpieces were subjected to cold plastic deformation by 60%, then processed by grinding to the required dimensions to measure their magnetic characteristics on a Remagraph C-500 magnetic measuring complex. Then the samples were annealed at different temperatures from 100 to 900 °C, holding for one hour and subsequent cooling in air. Final dimensions of samples amounted to 65,00 x 5,45 x 5,45 mm. The magnetic properties of the test samples, such as remanent magnetic induction (Br), coercive force (Hc), maximum magnetic permeability (µmax), maximum magnetic field strength (Hmax), maximum magnetic induction (Bmax) and maximum magnetization (Jmax), were measured on magnetic measuring complex Remagraph C-500. The remote induction sensor method was used as a reference method for measuring magnetostriction and magnetostrictive sensitivity. The sample was placed in a vertically standing solenoid and remagnetized by a quasi static magnetic field, the frequency of which is less than 0.1 Hz, with a maximum current in the solenoid windings of 60 A, which provides a field of up to 3000 Oe. A quartz rod, which has a low coefficient of thermal expansion, transmitted the magnetostrictive elongation of the sample on a permanent magnet, which is located in a remote coil induction sensor to eliminate the influence of the magnetic field of the solenoid. 3. Results and discussion In the Fig. 1. it can be seen that the coercive force decreases by a factor of 25 with an increase in the annealing temperature; in the temperature range of 300 – 400 degrees, a relatively sharp drop in the coercive force is observed. These changes are related to the rearrangement of the nickel domain structure during annealing. This significant change is due to the combined effect of a decrease in internal stresses, a decrease in the dislocation density, and an increase in the average grain size as a result of recrystallization. All these factors lead to an increase in the size of the magnetic domains in the material and the mobility of the domain walls. An increase in the magnetic permeability of nickel is also visible, starting from 400 degrees, with an increase in annealing temperatures, which is true since the coercive force decreases. In addition, the Rayleigh coefficient increases, which characterizes the dynamics of nickel magnetization and shows the contribution of irreversible processes during magnetization.