Results are presented of an on-going study of structure and solute redistribution in ribbon cast Al-Cu and Mg-Zn alloys. Regions found in these ribbons are (1) an apparently chemically homogeneous coarse-grained zone adjacent the chill, (2) a transition cellular region, and (3) a dendritic zone, usually equiaxed. In both alloys, structure in the equiaxed region becomes coarser with increasing distance from the chill. In Mg-Zn alloys, the amount of nonequilibrium second phase increases essentially linearly with distance in the cellular and dendritic regions. Scanning transmission electron microscopy can accurately measure solute distribution across rapidly solidified cells or dendrites, but the possibility of surface compositional changes during specimen preparation must be recognized.

The local electronic structures of representative amorphous alloys have been calculated using the SCF-Xα-SW cluster molecular orbital method. Prototype cluster models have been constructed for Cu-Zr and Pd-Si alloys which exemplify two major classes of binary (A-B) glass-forming systems, namely: (1) metallic glasses based on noble or transition elements (e.g., A=Cu) toward the right of the periodic table and transition elements (e.g., B=Zr) toward the left of the periodic table; (2) metalloid glasses based on transition elements (e.g., A=Pd) toward the middle of the periodic table and nonmetallic elements (e.g., B=Si) toward the right of the periodic table. The calculated electronic structures are in good quantitative agreement with, and provide an interpretation of, published photoelectron spectra for the above amorphous alloys.

Fe-C-base alloys were rapidly cooled from the liquid and then reheated from ambient temperature. In addition to the transitional elements (V,Cr,Mo,W), B was added as third element to substitute C. A systematic approach to the understanding of phases and microstructures, which form under these conditions is the purpose of this work. This includes the considerations of forming ability and thermal stability of metallic glasses. Three aspects require attention: a) absolute stability of the glass phase, b) relative stability i.e. the difference of Free Energy between the amorphous and particular crystalline phases, c) kinetic stability based on the rate and mechanisms of crystallization reactionsincluding the rate determing diffusion process. Light and electron microscopy and electron diffraction were used for the analysis of the structure of the alloys.

The variation of ac magnetic properties along the length of melt-spun Fe-based amorphous ribbons was examined in relation to the variations of the roller surface temperature and the ribbon thickness. The results indicated that the lengthwise variation of magnetic properties strongly depends both on the roller surface temperature and the ribbon thickness. The critical cooling rates at which core loss begins to increase were determined from the relationship between core loss and cooling rate. For ribbons cast at lower cooling rate than critical cooling rate, the finedomain patterns were usually observed on the free surface. From the disappearance of the fine-domain pattern and the remarkable decrease of core loss by removal of the surface layers, it is ascertained that the surface layers deteriorate magnetic properties.

The a.c. magnetic properties measured at 60 Hz are found to be strongly affected by ribbon thickness and annealing temperature. These magnetic results are further characterized by observations on magnetic domain structure, crystallization, stress relaxation, and ribbon surface finish.

Several new magnetic amorphous alloys containing early transition metals (TE) and having reduced metalloid (M) content have been melt spun. Some properties of three examples of this new class, 1) Co80Nb14B6, 2) Co84Nb10B6, and 3) Fe81Nb5B14, are presented. The dominant late transition meta1 (TL) content assures an appreciable magnetic moment while the presence of an early transition metal significantly enhances the stability against crystallization. Crystallization temperatures are 1) 742K, 2) 698K, and 3) 762K for the three alloys, respectively. X-ray diffraction patterns show the materials to be amorphous and to exhibit a large-r correlation length (approximately 2.0 A) that is shorter than is typiclly observed in TL80M20 glasses containing more than one transition meta) species (approximately 2.3 − 2.5A). The coercivities of the glassy compositions range from 30 to 70 m0e.

A method is proposed to calculate the crystallization behaviour of multicomponent metallic glasses with several phases. Various geometric shapes of precipitate can be considered. The model also takes into account changes in concentration which arise during precipitation.

In amorphous iron-chromium alloys magnetic contraction is superimposed on the thermal expansion. Depending on the proportion of antiferromagnetic chromium the resultant coefficient of expansion is either positiv, negative or zero. The chromium content also changes the Curie temperature. Relaxation processes have a marked effect on the thermal expansion. Long term and short term expansion behaviour was compared and discussed. In addition the crystallization behaviour and mechanical properties of the alloys are reported.

The influence of Cr, Mn, Co and Ni on the thermodynamic properties (molar heat of fusion, heat of crystallization and melting temperature), crystallization behaviour and hardness was studied in (Fe1-xMx)83B17 as a function of the x content. The crystallization behaviour can be described by three parameters which enables an extrapolation to longer times.

Equilibrium vapor pressures of dilute solutions of hydrogen in glassy Pd.80Si.20 have been measured from 10–90°C and at hydrogen pressures P of 1–100 torr. Under these conditions the ratio of hydrogen to alloy, x as determined by a volumetric method, reaches a maximum value of 0.0070. Over this range of x, the system exhibits a positive deviation from Sieverts' Law; isotherms were analyzed in terms of Lacher's modified statistical mechanical theory of hydrogen in palladium. The data were used to calculate relative partial molar enthalpies, excess entropies, and excess free energies for the formation of the solid solutions. The thermodynamic properties were found to vary with hydrogen content over the composition range studied.

The dilatation caused by the sorption of H and D in amorphous samples of melt-spun Pd82Si18 and sputter-deposited Pd81Si19 has been measured at room temperature for ambient charging pressures P up to 760 torr. By comparison with the strength of the Gorsky relaxation, it is concluded that (a) the dilatations per hydrogen and deuterium atom are identical and independent of concentration and (b) the non-linearity of the dilatation vs. p1/2 isotherms is due solely to a deviation from Sieverts' law. The isotherms exhibit a distinct isotope-dependence, of a similar nature to that for crystalline Pd. A sputterdeposited film is found to dissolve more H or D than a melt-spun ribbon, due possibly to a less structurally-relaxed configuration.

Several metallic glasses in the form of ribbons were screened for activity as hydrogenation catalysts. Pd80Si20 and (Ni50Fe50)80B20 showed activity in reducing cyclohexene. Pd 80 Si20 was further examined for differences between the glassy and crystalline phases in the selectivity shown during hydrogenation reactions of n-hexenes, phenylethyne, α-pinene, and cyclododecene. No significant differences were found for catalytic selectivity in regard to cis-trans isomerization, double bond migration, and stereochemistry of addition under the reaction conditions used. Minor differences were observed in hydrogen-deuterium exchange.

Rapidly quenched short fibers of Fe–8Al and Fe– 8Al–XZr (X = 0.1, 0.2, 0.4, and 1) alloys were produced by the Pendant Drop Melt Extraction Process, (PDME) to explore the feasibility of producing intermediate temperature, oxidation resistant iron base alloys. The fibers had a diameter of 20 to 50 μm and ranged in length from 2–5 mm. The cooling rate was insufficient to retain zirconium in solution in the Zr-containing alloys, resulting in precipitates of the type Fex(Zr,Al) having differing compositions at the grain boundaries and within the matrix. No precipitates were observed in the FeAl alloys. The precipitates were uniform in distribution and size (nominally 0.1 to 0.3 μm diameter). Grain boundary precipitation and precipitate size both decreased with decreasing Zr contents.

The characteristics of localized deformation in amorphous metals are reviewed. All the available evidences seem to suggest that dislocations are responsible for shear localization. These dislocations seem to require a stress concentration for their nucleation. Once nucleated, they are capable of producing both forward and reverse shear in a narrow band, much like the dislocations in crystalline materials.

The mechanical properties hardness, tensile strength and fracture toughness of (Fe100−x Mx )83B17 glasses were measured for different alloying con en s and heat treatments. In the as quenched state the hardness is influenced mainly by changes in the metal-metalloid bonding. The fracture toughness is dependent on the alloying elements as well as the actual state of the glass. Heat treatment of the glass thus hardly influences the hardness whereas the toughness decreases strongly and significant changes in the fracture surface occur. Calorimetric observations suggest that structural relaxation is the primary reason for this behaviour although some effect of annealing out of internal stresses must be present.

Deformation induced dilatations were measured on a Pd-Cu-Si glass by a differential dilatometric method during crystallization. At large pre-strains, these dilatations are large and of the order of 20%. Fracture surfaces of specimens in compression show either the characteristic features of tensile separation or evidence for repeated nucleation of fracture. Rubbing was observed only in a small fraction of a fracture surface.

In this· investigation we have systematically studied the brittleness and the atomic structure in an Fe(SiBC) alloy. Different amounts of hydrogen have been dissolved in the alloy. It has then been studied at different cooling rates.

Hydrogen gas of different partial pressures was dissolved into the melt. The alloy was then rapidly quenched by a chill block melt spinning method. The cooling rates were changed by changing the velocity on the chilling roll. The brittleness and the atomic structure were examined by bending tests and x-ray diffraction.

X-ray diffractions showed that the ribbons were amorphous when the cooling rate was sufficient. Amorphous ribbons without any hydrogen were ductile, crystalline ribbons of this alloy were brittle. The ribbons with dissolved hydrogen and amorphous structure were brittle even at small amounts of hydrogen. At the highest cooling rates the ribbons with low hydrogen content were ductile. There seems to be a connection between the hydrogen content and the amorphous ribbons ductility. The hydrogen content only has a slight influence to amorphous structure.

Amorphous surface layers produced by bonding metglas ribbons onto steel specimens were tested for their resistance to fretting. Friction and weight loss were determined and the worn surfaces were examined optically. There was no general tendency towards a better wear resistance of the tested amorphous metals as compared to crystallized metals or to a simple structural steel. The results will be discussed.

Six amorphous metals have been tested in liquid metal environments or while charging with hydrogen. Differences in sensitivity to each environment are correlated with fractographic features. Evidence in support of enhanced shear as the mechanism of environmental cracking is presented.