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Mössbauer spectra were obtained for α and β-Al-Fe-Si intermetallic compounds, which are usually detected as precipitates in commercial grade Al metals. The samples were prepared by two methods, electrolytic extraction of precipitates from Al ingots and direct melting of appropriate amounts of raw materials. By the latter method, pure compounds have been obtained, whose spectra can be used as the standard spectra of these compounds to analyze the Mössbauer spectra of Al alloys.

Two tungsten powders have been treated with small concentrations of sintering activators to provide for enhanced low temperature sintering. The experimental study focused on the determination of the processing effects on properties such as sintered density, grain size, hardness, and strength. Variables in the plan included tungsten particle size, type of activator, amount of activator, compaction pressure, and sintering temperature. The sintered density is found to have a dominant effect on strength and hardness. The various processing variables are analyzed in terms of their effects on density. At high sintered densities, grain growth acts to degrade the strength. Additionally, the nature of the sintering activator influences the fracture strength. In this study optimal strength occurred with a 0.7 μm tungsten powder treated with 0.29 wt pct Ni, sintered at 1200 °C for one hour. The resulting density was 18.21 g/cm3, with aR A hardness of 69 and a transverse rupture strength of 460 MPa.

Flinn’s model of short-range order hardening in fee binary solutions has been extended to take second-neighbor pair interactions into account. First and second neighbor pair probabilities are evaluated in the Tetrahedron-Octahedron approximation of the cluster variation method as a function of concentration and temperature, and for various values of the ratio of pair interactions. Predictions of the present model are found to differ significantly from those of the Bragg-Williams model used heretofore.

The 100 meter drop tube at NASA’s Marshall Space Flight Center has been used for a series of experiments with niobium-germanium alloys. These experiments were conducted with electromagnetic levitation melting in a 200 torr helium environment. Liquid alloys experienced large degrees of undercooling prior to solidification in the drop tube. Several interesting metastable structures were observed. However, the recalescence event prevented extended solid solubility of germanium in the A-15 beta phase. Liquids of eutectic composition were found to undercool in the presence of solid alpha and solid Nb5Ge3.

An X-ray technique for the measurement of internal residual strain gradients near the continuous reinforcements of metal matrix composites has been investigated. The technique utilizes high intensity white X-ray radiation from a synchrotron radiation source to obtain energy spectra from small (10-3 mm3) volumes deep within composite samples. The energy peak positions satisfy Bragg’s law and allow determination of the lattice parameter. As the probe volume is translated, the peaks of the spectra shift and are used to infer lattice spacing changes and thus strains with a precision of 10-3 to 10-4 (depending on the sample grain size/probe volume ratio). The viability of the technique has first been tested using a model system with 800 μm A12O3 fibers and a commercial purity titanium matrix. For this system (which remained elastic on cooling), good agreement was observed between the measured residual radial and hoop strain gradients and those estimated from a simple elastic concentric cylinders model. The technique was then used to assess the strains near (SCS-6) silicon carbide fibers in a Ti-14Al-21Nb matrix after consolidation processing. Reasonable agreement between measured and calculated strains was seen provided the probe volume was located 50 μm or more from the fiber/matrix interface. Close to the interface, the measured elastic strains were smaller than anticipated, due to relaxation of the residual stress by plasticity and radial cracking during sample cooling.