A matrix isolation technique for the investigation of infrared absorption spectra of molecules of hightemperature species trapped in a pseudo- gas phase'' is described. The spectra of the dichlorides of zinc, cadmium, and mercury in argon, krypton, and xenon matrices are reported. Presence in the gas phase of dimers of zinc chloride and mercuric chloride is noted. An absorption band, previously reported as due to the degenerate bending motion of zinc chloride, is attributed to zinc dimer. (auth)

The martensite burst transformation was studied in single crystals of iron containing 31.7% nickel. It was found that the morphology of the transformation was greatly simplified in crystals that had heen strained plastically prior to transformation. This simplification made possible detaiied crystallographic studies of the morphology of the transformation. These studies showed that the autocatalysis responsible for the burst transformation had its origin in a mechanical stimulation (coupling) between certain variants of the habit plane that were geometrically oriented such that the stress induced by transformation on one aided transformation on the others. In both strained and unstrained crystals, the most effective mechanical autocatalysis was observed to be between groups of four nearly parallel pianes whose poles clustered about common ( 110) directions. In the transformation of strained crystals, the operation of certain of these groups was favored. These were the groups whose planes were nearly perpendicular to the active slip plane, but did not include the group whose poles clustered about the Burger's vector of the active slip system. This behavior was taken to be a consequence of the anisotropic substructure introduced during deformation. Because of the enhanced transformation by certain groups in strained crystals, the frequency of secondary …

Techniques for forming polycrystalline LiF from the melt and for fabricating test specimens were developed and evaluated using single-crystal LiF as a control. Large -grain polycrystalline specimens tested in fourpoint loading always showed some plastic deformation (0.078 to 0.798%) before fracture, but the plastic flow was sharpiy reduced from that of single crystals. An etch was developed revealing dislocations on all crystallographic faces of LiF. Details of plastic deformation in polycrystalline material were investigated. Deformation was inhomogeneous among the grains of an aggregate because of differences in orientation with respect to the applied stress, also within individual grains because of interactions between adjoining grains. Grain boundaries were barriers to slip, but stresses resulting from slip in one grain were transmitted to neighboring grains and often caused local deformation near the boundary. Because of local stresses, local slip systems operated although the resolved shear stresses on them from the applied load were below the critical yield stress. In one case, slip occurred on an (010) plane. Three-grain junctions were areas of high residual stress. Fractures originated at boundaries at or near 3-grain junctions, not as a result of inherent boundary weakness but rather because of high stresses developed at the boundary. …