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We have studied the electrical properties of dislocations, stacking faults, and precipitates produced during 1200 °C aging of crucible-grown silicon. The defects were examined by SEM in the charge collection mode, at temperatures from 77 to 300 °K. Undecorated Frank extrinsic stacking faults exhibit defect energy levels in the upper half of the gap (∼Ec−0.1 eV). The partial dislocations bounding these faults possess energy levels lower than Ec−0.3 eV. Finally, precipitates are observed to act as microplasma sites at low (T<300 °K) temperatures.

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The compressive deformation behavior of polycrystalline iron-aluminum alloys has been investigated (i) at 298 OK for specimens heat treated in various ways and containing from 22.0 t o 31.7 atyo Al, and (ii) from 77 to 655 OK for well-annealed specimens containing 26.6 atyo 81. Alloys which possess significant DO, type long range order exhibit marked composition and temperature dependent variations in deformation behavior. Specifically, those containing 2 27 atyo A1 exhibit two linear and one parabolic deformation stage at 298 O K . The linear stages are shown to be a result of the production and motion of DO, type superlattice dislocations. The absence of these stages in well-annealed specimens is attributed to the lack of thermal assistance for the DO, superlattice dislocation nucleation process. The flow stress levels which characterize the two linear stage behavior agree with calculations of the stresses required for production of antiphase boundaries. Results obtained from quenched specimens are in agreement with the above conclusions, and the changes induced by quenching are in accord with calculations of the effect of thermal antiphase boundaries upon dislocation motion.

The adiabatic, elastic stiffnesses of five f.c.c. Ni-Co alloys in the range from 10 t o 62% Co were determined by the ultrasonic pulse-echo technique a t temperatures between 77 and 300 OK. As Co is added to Ni the bulk modulus increases linearly while (Cl, -CI2)/2 and C,, decrease and increase, respectively. The alloy stiffnesses were extrapolated to lOOq/, Co to yield the following estimates for the stiffnesses of f.