Submitted to Illinois Inst. of Tech., Chicago. A He/sup 3/ cryostat was built to measure the specific heat of rare earth metals which have a component, at low temperatures, attributable to the electrons in the incomplete 4f shell. The specific heat of dysprosium from 0.4 to 4.2 deg K was measured. Pertinent theories about specific heats are outlined. The apparatus included the cryostat, vacuum and He/sup 3/ systems, calorimeter, carbon thermometer, heater, and magnetic thermometer. The experimental procedure is described and results are presented in graphic and tabular form. The specific heat rose sharply below 1 deg K. An anomalous hump was centered about 2.35 deg K. (M.C.G.)

None

Polycrystalline aluminum-copper alloys containing 4 and 5% copper were given heat treatments designed to develop dispersions of Al/sub 2/Cu precipitate particles of various sizes and distributions. Tensile tests were performed on the dispersion hardened alloys at 4.2, 77, 90 and 114 deg K to determine the strain rate and temperature dependence of the flow stress. The intersection analysis of the tensile data showed that the dispersed particles significantly increase the average effective forest dislocation density produced for a given amount of strain. The increased dislocation density was found to be in qualitative agreement with selected electron-microscope observations of the deformed structure of the alloys. Estimates of contributions to the flow stress arising from effects coincident with the intersection of dislocations and those associated with the build-up of long range stress fields were made. The major strengthening contribution of the dispersed particles during plastic deformation is shown to be due to an increase in the dislocation density associated with relatively high density tangles of dislocations observed to be localized near particles and groups of particles. (auth)