Characterization and Analysis of Nanocrystalline Soft Magnetic Alloys: Fe Based

Abstract

Soft magnetic nanocrystalline alloys have been widely analysed and studied during the past years. However, optimisation of specific chemical compositions is still being developed. The applicability of these soft nanocrystalline alloys depends mainly on the presence of the desired nanocrystalline phases within the alloy. In this study, the analysed alloys are manufactured by mechanical alloying. The analyses performed on the samples include a microstructural analysis, a thermal analysis, and a complementary functional analysis in the form of the thermomagnetic response of some samples. Regarding Fe-based alloys, thermal stability for samples containing B was higher than those containing P (crystal growth peaks in the range between 895–905 K and 775–800 K respectively). The higher magnetization of saturation, Ms, was found in Fe–Mn alloys, whereas the addition of boron provoked a decrease of Ms and the nanocrystals size.

Two Fe-Zr-B-Cu Nanocrystalline Magnetic Alloys Produced by Mechanical Alloying Technique

“…Thus, the activation energy corresponds to the crystal growth mechanism. In nanocrystalline alloys with similar composition, the same phenomenon was detected [25][26][27][28][29][30][31][32][33][34]. At high transformed fractions, the degree of transformation slows down and the local activation energy decreases [44], probably due to the higher influence of the diffusion as main mechanism.…”

“…In this case, by applying the random anisotropy model, Hc depends on D 6 because the domain wall effect diminishes, and each grain behaves as a single domain. Thus, crystalline growth should be avoided, and the crystallisation temperature is a limiting temperature for the application of these alloys [26]. It should be remarked that as the Fe/B ratio lowers, the main crystallisation peak is shifted to higher temperatures (about 20 K).…”

“…In Fe-based alloys, with a minor addition of Cu, values ranging from 177 to 233 kJ/mol were calculated [37]. Thus, the identification of the process of crystallisation or as crystalline growth is usually performed while taking into account the room temperature nanocrystalline state [26,34]. Likewise, the formation of borides is found at higher temperatures when compared with those of bcc Fe-rich crystallisation [38,39].…”

An Extracellular Matrix-like Surface for Zn Alloy to Enhance Bone Regeneration

“…To avoid physical pain and additional financial expenditures from removal surgeries, biodegradable metals have attracted considerable attention in recent years. These metals are magnesium (Mg), iron (Fe), zinc (Zn), and their alloys. , Mg-based alloys with low corrosion potential generally degrade too fast, inducing hydrogen gas pockets and an alkaline microenvironment that inhibit bone integration. , Fe-based alloys have the highest corrosion potential among the three biodegradable metals; however, their degradation products (e.g., Fe 3 O 4 and FeOOH) are difficult to further degrade and metabolize, resulting in actually slow degradation rates. , Zn has a standard electrode potential of −0.763 V, which is much higher than that of Mg (−2.372 V) but lower than that of Fe (−0.447 V), providing a useful degradation rate, without the challenges faced by Mg and Fe alloys. Zn alloys are reported to have low elastic moduli (about 70 GPa), which are closer to that of natural bone (10–30 GPa), compared with stainless steel, cobalt alloys, or titanium alloys. , Furthermore, Zn is an essential trace element that serves as a catalytic cofactor in DNA and RNA-polymerases during nucleic acid synthesis and regulates the sequences of signal molecules and mediators, resulting in accelerated differentiation of osteogenesis-related cells in vitro and osseointegration in vivo .…”

“…8,9 Fe-based alloys have the highest corrosion potential among the three biodegradable metals; however, their degradation products (e.g., Fe 3 O 4 and FeOOH) are difficult to further degrade and metabolize, resulting in actually slow degradation rates. 10,11 Zn has a standard electrode potential of −0.763 V, which is much higher than that of Mg (−2.372 V) but lower than that of Fe (−0.447 V), providing a useful degradation rate, without the challenges faced by Mg and Fe alloys. Zn alloys are reported to have low elastic moduli (about 70 GPa), which are closer to that of natural bone (10−30 GPa), compared with stainless steel, cobalt alloys, or titanium alloys.…”