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Fe-Ni alloys containing 28 to 33 wt pct Ni have been studied by transmission electron microscopy and by selected area diffraction to elucidate the phenomenon of the apparent deviation of the twin interface from the twinning plane 112m. Trace analyses of the twin interfaces are reported for 35 cases. Deviations of the twin trace, as projected onto the image plane, of up to 46 deg from those expected from 122m transformation twins were observed. Contrary to previous interpretations, the conclusion of this study is that the deviations are due to the uncertainty of the orientation of the foil surface with respect to the electron beam. Thus, it has not been shown explicitly that this phenomenon provides a basis either for invoking multiple lattice invariant shears or for explaining habit plane scatter.

Electron microscopy was used to investigate the effects of alloying element content and quenching rate on the extent of precipitation during quenching and the resulting type of corrosion attack of naturally aged Al-Cu-Mg-Mn, Al-Cu, Al-Cu-Mg and Al-Cu-Mn alloys. Magnesium addition to Al-Cu led to S-phase (Al2CuMg) grain boundary precipitation and development of dislocation loops of the condensed vacancy type. This appears attributable to the greater affinity of magnesium atoms for copper atoms than for vacancies. Manganese, in the presence of copper and magnesium, retarded precipitation, apparently because of its high affinity for vacancies, lowering the number of unassociated vacancies available for long range diffusion. While increasing as-quenched strengths, this association apparently has the effect of developing grain boundary regions with steep electrochemical potential gradients, which appear responsible for susceptibility of the alloy to intergranular corrosion. It is concluded that precipitation phenomena which control the hardening and corrosion behavior of these alloys are related to the relative binding energies between the several solute elements, the affinities of these individual elements for vacancies, and the ratio of the atomic concentrations of the solute elements.

Transmission electron microscopy, quantitative optical microscopy, and texture studies were made on swaged and recrystallized titanium wire of three impurity contents: zone refined, a special lot of intermediate purity, and commercial A-70. The electron microscopy studies revealed that a) during recrystallization a number of processes overlap, and b) during grain growth there occurs a decrease in the dislocation density within the grains along with the increase in the average grain size. The quantitative microscopy studies indicated that the linear intercept grain size distribution is approximately log normal and that for a given mean grain size the distribution is relatively independent of the combination of annealing time and temperature used to obtain it. Moreover, there exists a range of grain sizes in space, the numbers of grains in each class interval changing with increase in grain size. The so-called grain shape factor decreases with increase in mean grain size (annealing time) at a constant temperature and with decrease in temperature for a constant grain size. The texture of the as-swaged wire and the changes in the texture during grain growth are in qualitative accord with those previously reported for deformed and recrystallized titanium. Impurity content influences the degree of these various structural characteristics but not their substance.

Experimental data are presented on the influence of cooling rate on the strength and deformation of thin Ag-4 pct Pd brazed joints in Fe-3 pct Si. It is observed that increasing the cooling rate (via water quenching vs furnace cooling) from the braze temperature can cause a drastic reduction in the strength of cylindrical butt brazed joints with a thickness to diameter ratio less than 0.02. The decrease in fracture strength is attributable to residual stresses and plastic strain caused by rapid cooling. The nature of the fracture process is unaffected by the cooling cycle and is always observed to be ductile failure caused by the growth and coalescence of microscopic shrinkage voids. Using hydrostatic annealing treatments, it is possible to restore the strength of rapidly cooled joints to values above those for furnace-cooled joints. This increase in strength is associated with a decrease in the volume fraction of microvoids accompanying the hydrostatic anneal.