The effects of adding small amounts of phosphorus to amorphous Fe78Si9B13 alloys have been investigated. Substituting boron atoms by phosphorus improves the thermal stability of the glassy alloys. The optimum stability is reached at about 1.2 at. % phosphorus concentration. With respect to the soft ferromagnetic properties, the saturation induction increases rapidly with increasing phosphorus concentration, reaches a maximum around 0.1–0.2 at. % and then decreases upon further addition. The highest induction value was achieved with 0.1 at. % phosphorus after field annealing for 2 hours around 633K. The mechanical strength of the amorphous alloy is greatly reduced for phosphorus concentrations larger than 0.4 at. %.

Spark erosion provides a means for producing fine particles (5 nm to 75 um) of metals, alloys, and semiconductors. Since the powders are formed from liquid droplets solidified in a liquid dielectric, the rate of solidification of the particles can be very high, varying according to particle size and the dielectric used. This paper examines some effects of different dielectrics on the microstructures, magnetic properties,and crystallization characteristics of amorphous and crystalline metals. It is seen that these properties depend upon the quench rate provided by the dielectric. In the case of the organic dielectrics, the quench rate appears to be associated with specific properties of the dielectric.

The structure and dynamics of a-TiCu(D,H)1.7 and a-TiCu(D,H)1.4 have been examined by Fourier transform quadrupole echo DMR line shape and relaxation time measurements at 30.7 MHz. The quadrupole-broadened a-TiCu(D,H)x line widths narrowed appreciably above 300 K because of increased D mobility. Low temperature DMR spectra show that static quadrupolar broadening is larger for amorphous samples than for crystalline samples. Deuteron spin lattice relaxation is attributed to conduction electrons below 200 K and to quadrupolar interactions at higher temperatures where deuteron hopping becomes significant. The spin lattice relaxation times indicate that the deuteron mobility is larger by an order of magnitude in the amorphous material than in the crystalline counterparts. Results are compared with those from proton magnetic resonance in corresponding hydrides.

The isothermal devitrification by nucleation and growth of metallic glasses is usually analysed using the Johnson-Mehl-Avrami (JMA) equation: where x is the volume fraction crystallized after time t, K is a thermally activated rate constant, τ is the nucleation lag time, and n is the so-called Avrami exponent. If the nucleation conditions and growth morphology remain unchanged during the crystallization then n is a constant. There is ample experimental evidence that for the Pd-Si system the growth process is either eutectic or interface-controlled. Therefore, one expects n=3 for crystallization on pre-existing nuclei (zero nucleation rate) and n=4 for crystallization at constant nucleation rate, both for three-dimensional growth. When the growth dimensionality is decreased by one these values decrease stepwise by one as well.

Glassy metallic alloys are usually formed by bringing a small amount of the melt mechanically into good thermal contact with a heat conducting medium. Cooling rates of the order of 106K/sec can thereby be obtained. Despite the extensive use of laser treatment in many areas of technology the idea of using ultra short laser pulses to increase the cooling rate by many orders of magnitude is relatively new. The rates obtainable in metals as a result of laser irradiation have been estimated to be of the order of 1010 K/sec (for nanosecond laser pulses) in the critical temperature region of high nucleation rate and low viscosity. Some less sophisticated estimates for laser annealing of silicon with picosecond pulses yield values of 1012 – 1013 K/sec.. The recent measurements of the surface colour temperature in laser irradiated metals suggest cooling rates of the order of 1010K/sec in both nanosecond and picosecond regimes.

There exists a great need for the development of high-performance light-weight alloys for aerospace application. Application of rapid solidification processing (RSP) has shown a strong potential for the improvement of properties of existing alloys and also for the development of novel alloy systems with superior properties. The present paper reviews the Allied-Signal's activities in the development of high-performance lightweight alloys by RSP. Examples include (i) high temperature aluminum alloys, (ii) aluminum-lithium alloys and (iii) corrosion resistant magnesium alloys.

It has been repcrted that rapid solidification insproves the ductility of certain nickel aluminides. This work. was devised to test whether it gives addittinal improvement in a nickel aluminide containing both Fe and B. Small samples were solidified in free-fall or splat-quenced after free-fall. Their uicrostructure has been characterized, and the results of preliminary tests, which give a quantitative measure of mechanical properties, are discussed.

A study of the effects of high intensity excimer laser radiation (249nm.) of aluminum and an Al-Si alloy reveals a variety of intriguing surface topographical features. Important parameters determining these include the energy-density and the number of short-duration (≈22ns.) pulses. Specific attention has been devoted to determining the condition for the onset of surface melting, and the physical effects of further increasing the energy density. A study of the frozen-in surface wave structure has been used to determine the approximate solidification time and the solidification-front velocity. As well as overall surface melting, an interesting phenomenon is the localized melting occurring at precipitates which preferentially absorb the incident radiation. This phenomenon has been studied in an Al-Si alloy subjected to single and multiple pulses; the effect of the latter has been found to have a striking effect.

Martensitic refinement is observed in rapidly solidified high speed steel (M7) by introducing a short ‘thermal arrest’ during cooling. This is accomplished using microcomputer controlled electron beam deflection for the generation of preselectcd scanning patterns. Such a tcchnique provides a high degree of control over short-duration heating at high temperatures and thus facilitates the use of fast reaction rate kinetics. By programming a ‘thermal arrest’ in the austenite range it has been found possible to obtain a distribution of fine carbides within the solidification cells. These carbides, it was found, result in refinement of the martensitic structure.

Nucleation temperatures are calculated for the case of solidification in atomized metal droplets where spherical substrate particles act as nucleation catalysts. Following the method of Fletcher, the effect of substrate size on catalytic potency is illustrated, and the model is applied to the nucleation of bcc solid from pure, liquid iron containing oxide substrate particles as catalysts. Supercooling data from the literature are used to determine wetting angles for alumina, silica, and rare-earth oxide. Oxide particle-size distributions are then used to predict the supercooling behavior of atomized liquid droplets based on the probability that a given size of droplet will contain a particular size of substrate particle. A transition size regime is found separating droplet sizes undergoing very small and very large supercoolings, respectively. This is discussed in terms of the types and number densities of inclusions present during atomization of the melt.

Rapidly quenched ribbons (˜50m thickness) of Al-5wt.%Ti, Al-lwt.%B and a range of Al-Ti-B alloys have been produced by melt spinning under He atmosphere and the microstructures of the ribbons, following solidification and post-solidification heat treatment, characterized using analytical electron microscopy. In the Al-5Ti alloy, the coarse equilibrium primary phase (b.c.t. Al3 Ti) that is observed following conventional casting is replaced by fine (0.1–0. 2μm), cuboidal particles of a metastable cubic (Ll2) Al3Ti in melt-spun ribbon. These metastable particles form directly from the melt and act as nucleation sites for the solid solution which subsequently forms. A refined microstructure with an average grain size of 1–2μm results. A supersaturation of Ti is retained in matrix solid solution following solidification and a variety of solid state precipitate forms, including fine dispersions of coherent, metastable Al3 Ti particles, is observed to emerge during post-solidification heat treatment. For the Al-1B alloy, the coarse distribution of primary AlB2 particles in a chill-cast ingot is replaced by a fine, uniform dispersion of the metastable boride, α-AlB12, in the melt-spun ribbon. Attempts to induce a refined boride dispersion in melt-spun Al-Ti-B alloys have proved largely unsuccessful.

A rapidly solidified Fe-10Cr-8Al alloy that contained a dispersion of very fine MnS and Al203 particles was produced by a gas atomization/twin-roll quenching technique. The RS particulates were consolidated by hot isostatic pressing, and the consolidated alloy was hot forged, and then hot and cold rolled. Grain growth took place during primary recrystallization of the alloy; however, once primary recrystallization was complete, the dispersion of second phase particles was effective in pinning alloy grain boundaries.

Thin films produced by laser breakdown chemical vapor deposition from nickel and iron carbonyls and by implanting Ni foils with varying levels of C have been characterizea by transmission electron microscopy. Decomposition of Ni(CO)4 produces polycrystalline films of fcc Ni and metastable ordered nexaogonal Ni3C. This metastable phase is identical to that produced by gas carburization, rapid solidification of Ni-C melts, and ion implantation ot C into Ni at low;co ncentrations. Increasing the H2 content in the gas mixture during laser deposition reduces the grain size of the films significantly witn grain sizes smaller than 10 nanometers produced. Laser uecomposition of Fe(CO)5 produces films with islands of fcc gamma-Fe and finely dispersed metastable Fe3C (Cementite). In addition, the ferrous oxides Fe2O3 and Fe3O4 were found in these samples. Implants of C into pure Ni foils at 77°K and at a concentration of 35 at.% produced amorphous layers. Implants at the same dose at room temperature did not proouce amorphous layers.

Rapidly solidified titanium alloys containing carbon and erbium have been examined microstructurally in the as-quenched and aged conditions. Studies show that cubic erbia forms initially, but prolonged aging results in the formation of trigonal erbia. The formation of this phase is enhanced by the presence of carbon.

The A15 Phase forming V-Ga alloys were processed into ribbons and foils by rapid solidification techniques. Microstructures and phase transformation in these alloys by rapid solidification and succeeding heat treatment were investigated by x-ray diffraction and TEM. It is shown that equilibrium A15 phases can readily be suppressed by rapid quenching in these alloys. A significant grain refinement resulting from the rapid solidification also was observed. Microhardnesses of these alloys as a function of Ga concentration were determined.

In the pseudobinary system Nb(Rh1−xPdx)3, as in other similar alloy systems, a series of polytypic phases occurs which have related, closepacked structures with systematically varying stacking sequences. After rapid quenching from the melt, the stacking sequence of these polytypes is often changed.

A phase m-Nb(Rh.75Pd.25)3 of the PuGa3 type with a 12-layer stacking sequence has been prepared by RSP; this phase is probably metastable and displaces an equilibrium phase of the VCo3 type with a 6-layer structure. Occurrence of the m phase can be rationalized in terms of the sequence of the Jagodzinski notation (fraction of h-like packing) and the variation of the diffraction pattern with composition.

Electron beam rapid solidification of molybdenum-base high speed steels results in quenched-in metastable phases containing a high concentration of alloying elements. Thermal reprocessing of such material by momentary interaction with the electron beam results in decomposition of martensite at a rate ≈ 100 times faster than that occurring during conventional thermal treatment. It is postulated that this arises from a high concentration of 'defect cluster nucleation sites' during the rapid up-quenching. The product of short thermal treatment is a dispersion of 2–5 nm very fine precipitates identified using transmission electron microscopy as MC type carbides.

Binary W-Ni alloys of four different compositions were rapidly quenched into thin foils. Microstructures and hardnesses of the as-quenched alloys were studied by TEM and hardness measurements. The results from the microstructural study show that the W grains and particles undergo extensive refinement and that the grain size is much smaller than that obtained in conventional alloys. In addition, the formation of WNi and W2Ni, the low melting temperature intermetallic compounds in the W-Ni system, was readily suppressed by rapid quenching. The hardness increase in rapidly solidified W-Ni alloys appears to have originated from the microstructural refinement.

Fatigue properties of a wrought Ni-base superalloy treated by laserglazing and post heat treatments have been investigated. Tests have been run both by the rotating bend fatigue at 700°C and the vibration fatigue of turbine blades at room temperature. The results showed that the fatigue property of laserglazed specimens was obviously deteriorated because of resolution of γ′ phase and grain boundary carbide, interdendritic segregation of TiC and microcrack caused by thermal stress. However, suitable preheating and post heat treatment added before and after laserglazing can eliminate these defects and recover the fatigue life of this superalloy. Selected laser processing technology was applied to repairing blades rejected due to microcracks at trailing edge. The vibration fatigue life of blades repaired by laserglazing and post heat treatment was over two times as high as that of normal used blades with same service time.

Surface alloys with various compositions of Co, Cr and W on 20CrMo steel have been processed by controlling the ratio of thickness of plasma sprayed Co-Cr-W coating to laser melting depth. A formula has been suggested to evaluate the contents of surface alloying elements. With increasing the contents of Co, Cr and W in the surface alloy system, two hardness peaks occur at about 17Co7Cr3W and 52Co22CrgW corresponding to microstructure of M and γ-Co + M23C6 respectively. Wear experiments in media of air, 1N H2SO4 and 1% NaCl indicate that 17Co7Cr3W surface alloy has higher wear resistance in air, while 52Co22Cr9W better in the corrosive media under high load. In any case, wear resistance of the above two surface alloys are much better than that of plasma sprayed coating of Co-Cr-W.