Powder flakes prepared from 50 μm thick melt spun ribbons of Markomet 1064 (Ni52.5 Mo38 Cr8 B1.5 wt%) were shock consolidatedin the unannealed and annealed condition. The unannealed flakes (microhardness 933 kg/mm2) are amorphous while flakes annealed at 900ºC for 2 hours have an fcc structure with a grain size of 0.3 μm and microhardness of 800 kg/mm2. The shock consolidated amorphous powder compact (250 kJ/kg shock energy)shows no crystal peaks in an X-ray diffractometer scan. Compacts of annealed powder (400 to 600 kJ/kg shock energies) contain amorphous material (18-21%) which was rapidly quenched from the melt formed at interparticle regions during the consolidation process. The microhardness of the amorphous interparticle material is 1100 kg/mm2. Wear properties of the compacts measured in low velocity pin on disk tests show low average dynamic friction values (∿0.03). The 60 hour cumulative wear appears to correlate with the energy of shock compaction and surface porosity of the compacts rather than the metallic glass content.

Metallic glasses have good mechanical and magnetical properties. However they embrittle after annealing and/or low temperature testing. In this paper, we describe the rupture of atom probe tips using fracture mechanical measurements. We found boron rich areas which seem to be interconnected and more numerous after annealing and act as crack nuclei. The good correlation between the calculated and the measured size of the critical defect seem to confirm that the boron segregations are on the origin of embrittlement and gives good ground for further straightforward investigations.

The catalytic activity and selectivity of Pd80Si20, Pd35 Zr65 Ni30Zr70, Fe40Ni40B20, Fe85B15 and Cu50Zr50 alloy ribbons in their amorphous and crystalline states were studied in the hydrogenation of 1—hexene and phenylethyne, dehydrogenation of methylcyclohexane and dehydrocyclization of n—heptane. Pd80Si20 was found to be the most active of the alloy catalysts studied. Most alloys were more active amorphous than in the crystalline state; however, the catalytic selectivities of the amorphous and crystalline states of each alloy were identical.

Current understanding of the local atomic structure of amorphous materials is reviewed. Sane results of probing short—range order by selected techniques are cited to illustrate the degree of uniformity that exists on a local scale. Observations of phase separation and phase changes are described with particular emphasis on a temperature driven, reversible transformation of the local structure observed magnetically in several cobalt—base glasses. The manifestations and implications of such transformations within the glassy state are examined. Several examples pointing to quasi—crystalline and to non—crystalline (non—space filling) local structures are given.

The addition of cerium in parts—per—million quantities has been shown to be effective in inhibiting the annealing embrittlement of melt—spun amorphous ribbons [1]. The effects of cerium doping on magnetic domain structures are reported in this paper. Domain structures have been observed using the Bitter colloid technique on the free surfaces of asquenched ribbons, as well as on both surfaces of ribbonswhich have been thinned by electropolishing. In the binary and quaternary alloys, the optimum (in terms of mechanical properties) cerium content gives ribbons which are apparently free of quenched—in stresses, since they lack the commonly observed “maze domains” which are found for both undoped and excessively doped ribbons. In contrast, the ternary alloy, which shows little decrease in annealing embrittlement versus doping, is free of maze domains in the as—quenched condition, with or without doping. The effect on the former two alloys is interpreted in terms of enhanced stress—relief during the quench.

Magnetic after effects (MAE's) have been studied in Fe—base and Co—base metallic glasses. Fe—base amorphous alloys shcw large MAE's due in part to the high magnetoelastic energy (large λs) whereas Co—basealloys exhibit much smaller MAE's due to their low magnetostriction. A detailed study of the acntribution of the magnetoelastic energy to the MAE's was done on the Fe83–xCrxB17 and Fe83–x NbxB17 glass systems.

Amorphous ribbons (FeNi)78Mo4B17Si, made by melt—spinning technique were prepared as magnetic shielding materials. Cylindrical shields (~0.05mm thick) were fabricated by wrapping ribbons on 20cm long pyrex tubes with 45mm diameter. DC and AC (60Hz, 400Hz, 800Hz, 1 kHz) magnetic shielding data were obtained by following the modified ASTM (A698–74) procedure. For DC magnetic fields, Ni—rich shields showed maximum shielding values at lower applied fields (0.1 0e~l 0e), while Fe—rich shields showed maximum shielding values at higher applied fields (1~5 0e). For AC magnetic fields, the magnetic fields, the magnetic shielding effectiveness was also influenced by skin effect at shield' surfaces. By comparing the data to calculations from shielding theory, there is about 8% magnetic shielding effectiveness induced by skin effect at 1 kHz.

We prepared thin, amorphous, compositionally modulated films (CMF) by RF sequential co-sputtering with Co, B, and Fe targets. In principle this technique can produce controlled, small (<15 Å) scale modulations in composition. The in-plane anisotropies and coercivities of the CMF were more than one magnitude larger than those of typical thin, homogeneous, amorphous, alloy films (AF). The increase in anisotropy was growth induced and could be reduced by annealing to values comparable to those of amorphous AF. The coercivity, however, could not be significantly decreased by annealing, except in CMvF with the highest boron concentration. The stability of the coercivity might, therefore, be an observable consequence of the small scale composition heterogeneity.

The structure and superconducting properties of rapidly quenched Zr—Ni and Zr—V alloys have been studied by XRD,EXAFS spectroscopy,TEM,electron diffraction,ED, electrical resistivity and ac susceptibility measurements. Amorphous Zr66Ni34 ribbons quenched with different cooling rates were also examined by flux pinning measurements. Characteristic differences are observed in the flux pinning mechanisms of microcrystalline and amorphous samples. The temperature dependence of upper critical fields have been measured down to 0.4 K and the results are analyzed in terms of WHH theory.

Hysteresis loops and anisotropy energy constants are measured in a magneto—optical system that combines Kerr rotation and ellipticity to enhance signal strength. Temperature dependence of the polar Kerr effect is compared with the magnetization of the iron subnetwork in the mean—field approximation and good agreement is obtained. Perpendicular magnetic anisotropy is studied by magneto—optical methods, yielding the first two coefficients of the series expansion of anisotropy energy in terms of the angleof deviation from the easy axis.

The magnetic and structural properties of melt-spun Fe-R-B alloys are reviewed. The hard magnetic properties of these alloys are attributed to the presence of a highly anisotropic tetragonal phase Fe14R2B which in the case of ribbons occurs in very fine grains. The interachoot of domain walls with this fine microstructure leads to the observed high coercivities. The effects of partial substitution of iron, rare-earth and boron on the formation of Fe14R2B and on its magnetic properties are also discussed.

Iron/rare-earth/boron permanent magnet materials have recently been delveloped to reduce the need for the strategic element cobalt, which was previously the primary canponent of high-energy magnets. These materials are generally produced by annealing rapidly solidified ribbons or by conventional powder metallurgy techniques. This paper will report results from an analytical electron microscopy characterization undertaken to establish the relationship between the magnetic properties and the microstructure of two iron/rare-earth/boron (Fe/RE/B) alloys. Ribbons of Fe75Pr15B10 and Fe77Tb15B8 were produced by melt-spinning. To obtain optimum magnetic properties, both alloys were then annealed at 700°C, the FePrB ribbons for 6 minutes and the FeTbB ribbons for 90 minutes. Foils for transmission electron microscopy were prepared by ion-milling the ribbons on a cold stage and examined using a Philips 400T TEM/STEM equipped with an energy dispersive x-ray unit.

Low field (∿5 Oe)Magneto-Thermo-Gravimetric technique has been used to study the effects of substitution of Nd with Y, Gd, and Dy in melt-spun Fe77Nd15B8 alloys, and also to monitor the changes in the magnetic properties on heat treatment to achieve optimum magnetic hardening in these alloys. From VSM-measurements preliminary studies of the effect of substitution for Nd on the hysteretic loops are presented.

Phase stabilities of iron alloys at low temperatures are strongly infuenced by magnetic effect. The appearance of certain type of equilibria is often due entirely to magnetic contribution to the Gibbs energy of the pertinent phase. The appearance of the stable and metastable equilibria in fcc(Fe,Ni) alloys are discussed in terms of the magnetic interaction.

Rapidly solidified Co-Cr thin films with a perpedicular magnetic anisotropy have been extensively investigated as one of the most promising media for perpendicular magnetic recording system. Most of these films used to be prepared by conventional RF diode sputtering and vacuum evaporation methods. We have developed the Facing Targets Sputtering apparatus which is able to deposite the magnetic thin films without the bombardment by high energy particles to the substrate along with the capabilities to deposit films under wide range of argon gas pressure at high deposition rate. It has been found that the texture and crystallographic structure of the sputtered films are primarily dependent on the argon gas pressure and the films prepared by the Facing Targets Sputtering exhibit quite different properties from the films prepared by conventional methods. The films deposited in the argon gas at the low pressure on the plasma-free substrate using the Facing Targets Sputtering are composed of the fine polyhedral grains packed densely from the initial growth layer to the surface layer of the film. They show exellent c-axis orientation of hcp crystallites, smoother surface textures and the superior perpendicular magnetic anisotropy as compared with the films composed of so-called columnar grains deposited in the argon gas at the higher pressures using the conventional RF diode sputtering. These results imply that the sputtering apparatus which is capable to deposit Co-Cr films in the argon gas at relatively low pressure is indispensable for the preparation of superior perpendicular magnetic recording media. Therefore, the Facing Targets Sputtering apparatus seems to be quite suitable for this purpose. Further, we have proposed a new micro structural model with fine polyhedral grains obtained by our sputtering method, because this model will have the ideal structural characteristics for ultra high density perpendicular magnetic recording.

Electron beam surface melting has been used to study Al-Mn and Al-Mn-Si alloys subjected to a wide range of solidification conditions. Several of the reported equilibrium intermetallic phases are not found even at moderate growth rates. Beyond a composition-dependent critical velocity the equilibrium phases are all replaced by the quasicrystalline icosahedral and decagonal (T) phases. The icosahedral phase is favored over the T phase by higher solidification velocities. The addition of Si to Al-Mn alloys eliminates the T phase, but does not significantly facilitate the formation of the icosahedral phase by electron beam melting because the ternary α and β phases of Al-Mn-Si are able to grow rapidly into the electron beam melts.

We report the first Hall, and electrical resistivity study on rapidly quenched icosahedral Al-based alloys. The Hall coefficient is found to be negative and remains so for i(Al-Mn) alloys even for higher Mn concentrations. The magnitude and temperature coefficient of the electrical resistivity behaviour in these alloys is similar to those observed for amorphous metallic alloys. Thus, the conduction process in i(Al-based alloys) is essentially electronic but with a carrier mobility an order of magnitude smaller than that known for crystalline aluminium.

Surface melting of alternating Al/Mn layers on Al and Fe substrates by pulsed electron beams and laser is found by TEM to produce icosahedral Al(Mn). Interpreting the observed microstructures in terms of the calculated temperature histories places limits on the melting point of the phase (660 0C < T < 9600C), the time needed for its nucleation from the melt at 6600C (t < 50 ns), and the rate of quenching from thg liquid n needed to suppress formation of the competing T phase (-T > - 1 × 10 K/s).

Studies of phase formation in rapidly solidified Al-Mn alloys (composition range 18-22 at% Mn) show that an icosahedral phase is replaced by another noncrystallographic phase, a decagonal phase. The decagonal phase is another example of quasicrystal: It has a noncrystallographic point group (10/m or lO/mmm) together with long-range orientational order and onedimensional translational symmetry. The decagonal phase is an intermediate phase between an icosahedral phase and a crystal both from the symmetry and from the solidification condition points of view.

RSP of Al-rich Al-Mn alloys is known to produce several metastable phases, including (with increasing Mn content) supersaturated Al solid solution and two non-crystallographic phases, identified in the literature as an icosahedral phase (I) and a (probably) decagonal phase (T) with translational symmetry in one direction. The formation of these phases in the composition range from 8 to 30 at. pct. Mn has been studied in melt-spun and arc-furnace quenched alloys. The thermal transformation characteristics of all metastable phases were measured by DSC; transformation temperatures, enthalpies and activation energies were determined. At compositions from 17 to 20 at. pct. Mn, two transformations were observed. Noteworthy results include: smeared out (slow-onset) reactions, transformation temperatures dropping sharply toward lower Mn contents, transformation enthalpies rising steeply in the same range, and activation energies ranging from ~40 kcal/gmol for the low-temperature process (at ~763 K) to ~80 kcal/gmol for the high temperature process (~883 K).