Fe Co Based Nanocrystalline Alloys

Nanocrystalline FINEMET-type alloys (FeSiBCuNb ) having average grain diameter ~ 10 nm , obtained by the devitrification of rapidly solidified (typically 20 mm thick ribbons) amorphous alloys are attractive for applications due to their excellent soft magnetic properties e. g. – high saturation magnetic induction comparable with Fe-based amorphous alloys and large permeability as observed in Co-based metallic glasses. In Finemet type alloys the presence of small amount of Cu enhances the nucleation rate, while presence of Nb inhibits the grain growth, resulting in nano-crystallization which proved to be key factor for obtaining the particular ultra fine grain structure.

We report the influence of composition and very high transverse field annealing on the magnetic properties and structure of four FeCo-based amorphous and nanocrystalline alloys. The compositions (Fe50Co50)89Zr7B4 and (Fe65Co35)89Zr7B4 were investigated changing the Fe:Co ratio from 50:50 to 65:35. (Fe50Co50)85Zr2Nb4B8.5 was chosen to investigate Nb substitution for Zr in an FeCo-based alloy. This substitution is shown to increase the magnetostrictive constant, lambdaS, of the nanocrystalline alloy from 36x10(exp -6) to 54x10(exp-6). The composition (Fe65Co35)84Cr5Zr7B4 was studied to investigate the influence of Cr on intergranular coupling across the amorphous matrix. Samples of each composition were annealed in the amorphous state at 300 C and in the nanocrystalline state at 600 C. Field annealing was performed in 17T transverse field in an inert atmosphere. Frequency-dependent magnetic properties were measured with an automatic recording hysteresisgraph. Static magnetic properties were measured with a vibrating sample magnetometer. The mass-specific power loss of the alloys decreased with field annealing in both the nanocrystalline and amorphous states for some frequency and induction combinations. Furthermore, the hysteresis loops are sheared after field annealing, indicating a transverse magnetic anisotropy. The nanocrystalline (Fe50Co50)85Zr2Nb4B8.5 composition has a lower relative permeability than the other compositions.

Since the first synthesis of an amorphous phase in Au-Si system by rapid quenching of melt in 1960, a great large number of amorphous and glassy alloys were prepared up to date. Their alloy systems cover almost all metallic elements in the periodic table and can be classified to ferrous and non-ferrous alloy groups. Considering the present application situation and its future prospect of amorphous and glassy alloys, ferrous metal-based amorphous and glassy alloys are particularly important and attractive and their engineering importance has steadily increased toward the creation of a low-carbon society. Here we introduce the development examples of Fe- and Co-based amorphous and nanocrystalline alloys with unique morphologies such as wire, flaky powder and spherical particle and Fe-C base amorphous steels with new alloy compositions, in conjunction with their applications.

Reflecting the fast pace of research in the field, the Second Edition of Bulk Metallic Glasses has been thoroughly updated and remains essential reading on the subject. It incorporates major advances in glass forming ability, corrosion behavior, and mechanical properties. Several of the newly proposed criteria to predict the glass-forming ability of alloys have been discussed. All other areas covered in this book have been updated, with special emphasis on topics where significant advances have occurred. These include processing of hierarchical surface structures and synthesis of nanophase composites using the chemical behavior of bulk metallic glasses and the development of novel bulk metallic glasses with high-strength and high-ductility and superelastic behavior. New topics such as high-entropy bulk metallic glasses, nanoporous alloys, novel nanocrystalline alloys, and soft magnetic glassy alloys with high saturation magnetization have also been discussed. Novel applications, such as metallic glassy screw bolts, surface coatings, hyperthermia glasses, ultra-thin mirrors and pressure sensors, mobile phone casing, and degradable biomedical materials, are described. Authored by the world’s foremost experts on bulk metallic glasses, this new edition endures as an indispensable reference and continues to be a one-stop resource on all aspects of bulk metallic glasses.

Metallic (magnetic and non-magnetic) nanocrystalline materials have been known for over ten years but only recent developments in the research into those complex alloys and their metastable amorphous precursors have created a need to summarize the most important accomplishments in the field. This book is a collection of articles on various aspects of metallic nanocrystalline materials, and an attempt to address this above need. The main focus of the papers is put on the new issues that emerge in the studies of nanocrystalline materials, and, in particular, on (i) new compositions of the alloys, (ii) properties of conventional nanocrystalline materials, (iii) modeling and simulations, (iv) preparation methods, (v) experimental techniques of measurements, and (vi) different modern applications. Interesting phenomena of the physics of nanocrystalline materials are a consequence of the effects induced by the nanocrystalline structure. They include interface physics, the influence of the grain boundaries, the averaging of magnetic anisotropy by exchange interactions, the decrease in exchange length, and the existence of a minimum two-phase structure at the atomic scale. Attention is also paid to the special character of the local atomic ordering and to the corresponding interatomic bonding as well as to anomalies and particularities of electron density distributions, and to the formation of metastable, nanocrystalline (or quasi-crystalline) phases built from exceptionally small grains with special properties. Another important focus of attention are new classes of materials which are not based on new compositions, but rather on the original and special crystalline structure in the nanoscale.

Metallic (magnetic and non-magnetic) nanocrystalline materials have been known for over ten years but only recent developments in the research into those complex alloys and their metastable amorphous precursors have created a need to summarize the most important accomplishments in the field. This book is a collection of articles on various aspects of metallic nanocrystalline materials, and an attempt to address this above need. The main focus of the papers is put on the new issues that emerge in the studies of nanocrystalline materials, and, in particular, on (i) new compositions of the alloys, (ii) properties of conventional nanocrystalline materials, (iii) modeling and simulations, (iv) preparation methods, (v) experimental techniques of measurements, and (vi) different modern applications. Interesting phenomena of the physics of nanocrystalline materials are a consequence of the effects induced by the nanocrystalline structure. They include interface physics, the influence of the grain boundaries, the averaging of magnetic anisotropy by exchange interactions, the decrease in exchange length, and the existence of a minimum two-phase structure at the atomic scale. Attention is also paid to the special character of the local atomic ordering and to the corresponding interatomic bonding as well as to anomalies and particularities of electron density distributions, and to the formation of metastable, nanocrystalline (or quasi-crystalline) phases built from exceptionally small grains with special properties. Another important focus of attention are new classes of materials which are not based on new compositions, but rather on the original and special crystalline structure in the nanoscale.

This book presents recent advances and developments in control, automation, robotics, and measuring techniques. It presents contributions of top experts in the fields, focused on both theory and industrial practice. The particular chapters present a deep analysis of a specific technical problem which is in general followed by a numerical analysis and simulation, and results of an implementation for the solution of a real world problem. The presented theoretical results, practical solutions and guidelines will be useful for both researchers working in the area of engineering sciences and for practitioners solving industrial problems.