Phase formation, crystallization kinetics and properties of (Fe,Co)-based bulk metallic nanocomposites
Mechanical Properties of Metallic Materials and their Microstructural Origins
Final Report Abstract
The objectives of the project were attained. The main achievements are presented in the following: Starting from known BMGs, three new classes of glassy alloys were created: (Fe36Co36B19.2Si4.8Nb4)100-xCux, (Fe1-xNix)77Mo5P9C7.5B1.5 and [(Fe1-xCox)71.2B24Y4.8]96Nb4. Among the new created BMGs, the (Fe36Co36B19.2Si4.8Nb4)99.5Cu0.5 rods with 1 mm diameter and (Fe0.9Ni0.1)77Mo5P9C7.5B1.5 rods with diameters up to 2.5 mm may undergo plastic deformation under compression. The 1 mm diameter (Fe0.9Ni0.1)77Mo5P9C7.5B1.5 glassy rods show the largest compressive plastic deformation among the all known Fe-based BMGs described in literature. The mechanical behaviour and the mechanical properties were elucidated upon in-situ xray diffraction using synchrotron radiation. The “plasticity” of the Fe-based BMGs can be explained through the different elastic behaviour at the level of different atomic shells. Upon compositional variation the DC soft magnetic properties are kept or even enhanced (very low coercivity, high permeability, as well as flattening of the hysteresis loops upon annealing). The AC magnetic properties measured on ring-shaped castings have revealed a relatively low level of magnetic losses, much lower at 50 Hz or 60 Hz than those measured for the regular electrical steel. The anomalies in the magnetic properties of [(Fe1-xCox)71.2B24Y4.8]96Nb4 BMGs in function of Co content were studied and explained using the micromagnetic theory. For all glassy alloys the thermodynamics and kinetics of phase formation were studied and clarified. In regard with the original proposal, some aspects had to be amended during the work. In this way new insights were obtained and several unknown aspects were clarified: Cu addition to the base composition Fe36Co36B19.2Si4.8Nb4 enhances the plastic deformation only if the Cu level is lower than 1 at%, preferably 0.5 at%. In the same time the GFA decreases, maximum achievable rod diameter upon casting being 2 mm for a length of 5 cm. Despite the general believe, proved in fact only in the case of few compositions, in our case the Y additions did not enhanced the GFA. Moreover, the viscosity of the master alloy was drastically decreased and it seems that the global reactivity of the alloy is enhanced, making it very prone to extensive oxidation. However, in (Fe,Co)BYNb alloys it has a positive influence and the resulted (brittle) BMGs show very good soft magnetic properties. Despite the several literature data (and own experience), the fluxing with B2O3 did not enhance the GFA. Moreover, upon fluxing the liquidus temperature of the master alloy was drastically enhanced and the glassy samples were prone to crystallization directly upon casting. Such behavior was observed in the last year also by Prof. Teruo Bitoh (Akita Prefectural University, Japan, 2013).
Publications
-
“[(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4 metallic glasses with small Cu additions”, Metallurgical and Materials Transactions A, 42 (2011), pp. 1476-1480
M. Stoica, R. Li, S. Roth, J. Eckert, G. Vaughan, A.R. Yavari
-
“Thermal stability and magnetic properties of partially Co-substituted (Fe71.2B24Y4.8)96Nb4 bulk metallic glasses”, Journal of Applied Physics 109 (2011), 054901
M. Stoica, V. Kolesar, J. Bednarčik, S. Roth, H. Franz, J. Eckert
-
“New (Fe0.9Ni0.1)77Mo5P9C7.5B1.5 glassy alloys with enhanced glass-forming ability and large compressive strain”, Materials Science & Engineering A 560 (2013) pp. 575–582
A. Seifoddini, M. Stoica, M. Nili-Ahmadabadi, S. Heshmati-Manesh, U. Kühn, J. Eckert
-
“Atomic structure and magnetic properties of Fe–Nb–B metallic glasses”, Journal of Alloys and Compounds 586 (2014), pp. 189-193
I. Kaban, P. Jóvári, A. Waske, M. Stoica, J. Bednarčik, B. Beuneu, N. Mattern, J. Eckert
