Metallic glasses of composition Pd58.8U20.6Si20.6 can be transformed to a metastable single phase with quasicrystall ne order by thermal annealing. The icosahedral symmetry of this phase was verified by both electron and x-ray diffraction. Although the metallic glass can be formed over a broad compositional range the homogeneity range of this icosahedral phase is less than 1%. This indicates strong chemical ordering in the quasicrystalline state.

Different extended icosahedral structures are obtained from energy minimization and local symmetry Yh. The quasi fractal character of one of these is demonstrated from the quasi algorithm of definition, the gamma density of holes and the measured Hausdorff number ∂. The spectral dimension ∂ is measured and dimensions corresponding to higher derivatives are defined.

In spite of giving exceptionally low density and excellent machinability at relatively low cost, magnesium alloys have found only restricted application as engineering materials to date because of limitations in formability, corrosion resistance, strength and creep resistance. Although the very earliest work on record to employ rapid solidification as a means to enhance engineering properties was carried out on magnesium-base alloys, subsequent work employing more modern techniques has not, until very recently, been motivated by the need for alloy development. The present study combines a critical survey of relevant published work with an assessment of the potential of magnesium-base alloys for development by the rapid solidification route.

Rapidly quenched alloys differ from those that are conventionally solidified in the degree of supersaturation, the microstructure and the grain size. The quenching rate can thus be used to modify the mechanical properties. A fine grain size increases the hardness and ductility. The precipitation behaviour is modified by the high density of heterogeneous nuclei or high density of quenched in defects in that the rate of precipitation is increased. Discontinuous precipitation should make a significant contribution to the increase in strength as a result of the fine grain size.

The deformation behavior of a rapidly solidified Al-3.7%Li-O.5%Zr alloy has been investigated using transmission electron microscopy. Aging of the alloy in a conventional manner produces a homogeneous precipitation of δ' with small amount of heterogeneously distributed composite precipitates. The deformation behavior of the alloy in such aging conditions is dominated by the readily shearable δ', resulting in a pronounced planar slip. A homogeneous distrubution of composite precipitates promoted by double-aging treatment, however, alters the deformation mode to wavy slip by inducing the by-passing of dislocations around the shear resistant composite precipitates.

In recent years, interest in high temperature aluminum alloys has increased. However, nearly all the data available is for simple extrusions. This paper looks at the properties of sheet made from a rapidly solidified Al-10Fe-2.5V-2Si alloy. The sheet is made by direct forging followed by hot rolling, this is readily scalable, so allowing the production of large sheet. The room temperature strength and fracture toughness of the sheet are comparable to those of 2014-T6. The high temperature strength, specific stiffness and corrosion resistance are excellent. Recently, improved thermomechanical processing and new alloys have allowed higher strengths and fracture toughness values to be obtained.

Rapidly solidified (RS) Al-Er, Al-Nd, and Al-Gd ribbons were prepared by pendant drop melt extraction (PDME). The microstructures were studied in detail by optical and transmission electron microscopy. A wide range of microstructures are observed, including “conventional” RS type zones, a cellular structure surrounded by a degenerate eutectic and coupled (lamellar) eutectic structures. A bimodal precipitate distribution is seen in many areas of the ribbons. A series of isochronal heat treatments was conducted to determine the relative thermal stability of these microstructures, which were evaluated by Knoop microhardness measurements.

Using the arc-furnace hammer-and-anvil method, metastable alloys in the Al-rich portions of four Al-RE systems (10-30 at. pct. RE; Re = Gd, Ho, Er and Y) were prepared and examined by XRD. The principal results are: all equilibrium alloy phases [Al4RE (T phase), Al3RE (CN12 close-packed phases) and Al2RE (Laves phase)] have substantial metastable solid solubilities for excess Al; e.g., in the Al-Y system, L phase is extended from 66.7 up to 86 at. pct. Al, suppressing any formation of the Al3RE phase in that system.

For early RE elements up to and including Gd, T phase is favored; for alloy chemically intermediate RE elements such as Y, L phase is dominant and for late RE elements (after Ho), the CP phases are extended most. DSC work indicates the formation of additional metastable phases occurring during equilibration.

The Targets Facing Type of Sputtering (TFTS) system can deposit very dense films on substrates at a high rate without undesirable influences of the plasma. Using this system, Al films 0.7 ∿ 1.5 µm thick were deposited in an argon gas pressure PAr of 9.7 × 10−2 Pa.

The grains with irregular shape grew as PAr became high. However, the number of grains per unit area decreased and their size became small when the bias voltage to the substrate Vb was -40 V. Consequently, the film surfaces became smooth. The Al films became hardest at Vb of about -40 V and were twice as hard as ones prepared without the bias voltage.

The step coverage of these Al films was very satisfactory to the wiring of the integrated circuit (IC) by adjusting Vb and PAr at the proper values.

The attributes and requirements for rapid solidification (RS) are discussed and related to the characteristics of the titanium system. The extreme reactivity of liquid titanium requires the development of RS production methods tailored to this system. Compaction and processing techniques are presented followed by a discussion of the various alloy classes which have been produced by the RS approach: conventional alloys such as Ti-6Al-4V, rare earths, metalloids, eutectoid formers, beta alloys, amorphous materials, high aluminum alloys, aluminides, and other minor classes. Finally some thoughts on the future of this technology are presented.

Thermochemical treatments of titanium surfaces by laser are presented and the beneficial effects attainable eg wear resistance, corrosion resistance etc., discussed. It is shown that it is possible to produce titanium surfaces with load bearing capability.

Titanium alloys containing alpha matrices with various rare earth compound dispersions were prepared by melt extraction. The melt extracted material was HIPped, extruded, and thermally exposed to yield various microstructures including transformed beta and equiaxed alpha. Tensile and creep tests were conducted on material in the different microstructural conditions. Trends in mechanical behavior as a function of alloy chemistry and process history are discussed. The alloys with a transformed beta microstructure had superior creep resistance. Alloys containing dispersoids had better tensile ductilities compared with those which did not contain a dispersoid.

Portions of this work were carried out under Air Force Contract F33615-83-C-5034.

Rapid quenching of binary Ti alloys from the melt results in various metastable phases. A systematic study has been conducted in order to elucidate principles associated with the formation of metastable phases in binary Ti alloys resulting from rapid quenching. These metastable phases that include α’, α” phases, metastable β phase, and w phase are discussed with regard to their occurrence and the extension of a phase as a function of cooling rate. Effect of cooling rate and mechanical stress applied during cooling on metastable phase formation was investigated.

Titanium aluminide alloys with matrix compositions of essentially Ti3Al plus 0, 5, 7.5, and 10 a/o Nb and with and without rare earth elements for dispersoid formation were prepared. The alloys were rapidly solidified by melt spinning. Ribbon was consolidated by HIP and extrusion at temperatures below the beta transus temperatures of the alloys. The effects of processing conditions and dispersoid additions on room temperature ductility and fracture toughness were studied.

The microstructures of ordered Ti3Al-lZr (alpha2 +Zr) and Ti-Al-Nb alloys produced by ingot metallurgy (IM) and by rapid solidification (RS) are compared. The RS Ti3Al-iZr (alpha2 structure) alloy displayed small antiphase domains (APD) of 10–20 nm in the as-produced condition, but large grain size. The latter observation is rationalized in terms of the cooling history used to produce the material. The RS Ti-Al-Nb alloy exhibited an equiaxed microstructure. The IM Ti-Al-Nb material displays a complete change in microstructure between 1010°C and 1035°C, indicating a narrow alpha+beta phase field.

The microstructures of titanium aluminide alloys containing a rare earth oxide dispersion have been characterized using analytical electron microscopy. The alloys, based on Ti3A1 (alpha-2), contained 0 to 10.7 atom% Nb and 0.5 atom% Er. Alloys were rapidly solidified by melt spinning and were subsequently consolidated by HIP and extrusion. The microstructure of each alloy was examined in the as-cast, as-HIP'ed, and as-extruded conditions. A fine dispersoid spaced less than 100 nm apart was observed in ribbon aged at 750°C. The effects of processing conditions on the dispersoid distribution as a function of matrix chemistry were studied. Hot deformation was also examined to investigate the nature of the interaction between the dispersoids and the matrix during deformation.

Rapidly solidified Ti alloys containing rare earth metal dispersoids, such as La or Er, have excellent resistance to coarsening at elevated temperature (700–900°C). In particular, the coarsening of the dispersoid particles in RSP Ti-5Sn-3Y was studied; these particles were found to be Y5Sn3. The measured growth kinetics were found to be compatible with the modified LSW model; it was concluded from the observed parameters that in this alloy the diffusion rate of Y is the rate determining factor, providing a measurement of the diffusion coefficient of Y in a Ti matrix and yielding its activation energy Q = 272 kJ/mole.

Equiatomic TiNi alloy has been rapidly solidified by melt spinning. The M3 temperature of ribbon is depressed with respect to samples made from elemental powders. This phenomenon is related to grain refinement. Some of the ribbons have been crushed and the consolidation characteristics of the resulting pre-alloyed powder is compared with that of elemental blends. Sintering activity is higher in elemental compacts as a result of the dominant effect of the a]loy formation energy in elemental blends.

The improvements in the mechanical properties of nickel-base alloys that have been made possible by rapid solidification processing are reviewed. The results of processing by powder metallurgy, laser melting, low pressure plasma deposition and spray forming are examined. In general, the increased homogeneity obtained by rapid solidification allows for increased alloying and improved hot workability. The refined grain size improves the low and intermediate temperature strength, but leads to lower strengths at high temperature. For the high temperature applications, post solidification grain growth is required, as for example the directional recrystallization of powder metallurgy preforms. The development of a novel means of producing a fine dispersion from amorphous alloy precursors and the recent work attempting to improve the ductility of the intermetallic phases NiAl and Ni3A1 are also described.

Attempts have been made to study mechanisms of strengthening in the Ni68W22C8B2 and the Ni45CO20 Cr10MO4Fe5B16 alloy systems during their amorphous crysialline transitions. In the Ni68W22C8B2 system where amorphous particulates of varying sizes have been cons Ti a ed at high pressure and low temperature (3.6 MPa, and 673°K respectively), the initial stage of crystallization is marked by transformation of the localized regions of the specimen. These crystallized regions contain microcracks and voids. Microhardness measurements from the consolidated specimens indicate an increasing trend in the microhardness with decreasing particulate sizes. Premature failures of the consolidated specimen during tensile stress measurements have been attributed to the presence of microcracks and voids in these specimens. In the Ni45Co20Crl0Mo4Fe5B16 alloy system isothermal annealing of an initially amorphous alloy has been allowed to produce grains of varying sizes. The tensile stress measurements from these thermally annealed ribbons indicate two distinctly different functional relationships between the strength, σ, and the grain size parameter, λ. In the early stage of transformation where grain reach a maximum growth of up to 400 Å, the functional form of the strength, σ, with the grain parameter, λ, is σ = σ + K Log λ, where σO and K are constants. During latter stages of transformation, where grains larger than 400 Å have been formed, the strength, σ, varies with the inverse square root of the grain sizes. This latter relationship is analogous with the well known Hall-Petch relationships, which describes the strength, σ, as a function of the grain sizes in conventionally processed alloys.